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1999-2004 Mustang PI Intake Manifold Comparison

Created by Jay Walling / 7 min read
Date Created: 8/13/2022
Last Updated: 8/16/2024

The 4.6L SOHC engine found in the New Edge Mustang was improved in many areas over previous years. One of these updates included the intake manifold. This article will cover the primary differences between the OEM intake and the popular aftermarket designs.

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4.6L 2V Intake Manifold Comparison

Intake ManifoldPart NumberPeak HorsepowerPeak TorqueAvailable In Aftermarket?
Old FPP PI Intake ManifoldM-9424-P46244.0275.4No
New FPP PI Intake ManifoldM-9424-P46A233.6264.1Yes
Dorman Intake Manifold615-178222.4266.2Yes

Table of Contents

Product Links


History Of The PI Intake

On February 4, 2002, Ford issued a TSB (Technical Service Bulletin) for multiple Ford, Lincoln, and Mercury 4.6L SOHC engine models due to the plastic coolant crossover design on the intake manifold. This plastic construction would develop fatigue cracks and cause coolant seepage over time in the compromised areas. The fix was the same intake manifold but with a revised coolant crossover that was changed from plastic to cast aluminum. This redesign included a revised alternator bracket and the updated intake manifold.

1999-2004 Mustang Intake Manifold Differences  - 1999-2004 Mustang Intake Manifold Differences


Original Ford vs. Dorman Comparison

We will begin with the Dorman Intake manifold. This intake fits other Ford, Lincoln, and Mercury models and the 1999 to 2004 Mustangs with the PI (which stands for Power Improved) cylinder heads. Dorman supplies an intake manifold with pre-installed individual o-ring-style gaskets, alternator bracket, self-cutting screws, thermostat, thermostat gasket, and other miscellaneous hardware depending on the model of vehicle it's being used for. Some of the fastener locations do not have threaded inserts; this is where you will use the self-cutting screws that Dorman provides in the kit.

The only factory hardware that is re-used is the intake manifold to cylinder bolts, plenum to intake manifold bolts, and alternator bracket bolts. The intake runner design is different, and the manifold chamber is significantly smaller when compared to the Ford manifold. This does change where the engine makes peak horsepower and torque numbers.

Now, we can take a look at the Ford OEM intake manifold. This intake will be the same production intake from 2002 to 2004 Mustangs. No revisions have been made, and all of the factory hardware is reused. The intake that’s branded as Ford Performance is the same intake as the original, it’s just sold under the Ford Performance brand.

You will need to purchase new intake gaskets and a thermostat gasket with this intake, as the only pre-installed gasket is the plenum gasket. This intake will not affect horsepower and torque if you’re replacing an existing Ford PI intake.

1999-2004 Mustang Intake Manifold Differences  - 1999-2004 Mustang Intake Manifold Differences

Dyno Comparison Numbers

Alright, so now let’s get to the good stuff! Are there horsepower and torque differences between the two intake manifolds? Well, we are very fortunate to have the best tool in the industry to determine rear wheel horsepower and torque, which is a chassis dyno. The data we will share with you today is from our 2004 Competition Orange GT that has been featured on our channel in a full series titled Keeping Comp. During the restoration process, I put it back on the dyno with the Dorman intake manifold still in place. The car had already had a tune-up, and the check engine light was fixed from the baseline dyno. We had also switched out and added all of the parts associated with the build; that way, we would have an apples-to-apples comparison.


Dyno Technical Data

  • Cold Air Intake
  • Off-Road Mid-Pipe
  • Borla Mufflers
  • Aluminum Driveshaft
  • 3.73 Gears
  • 18x10 Inch SVE Series 2 Wheels
  • 285/35/18 Tires
  • SCT Strategy Tune For 93 octane Fuel
  • The Transmission Is 5-Speed TR3650, And The Pull Was Made In 4th Gear

1999-2004 Mustang Intake Manifold Differences  - 1999-2004 Mustang Intake Manifold Differences

With the Dorman intake, the car made 222.4 HP at 5200 RPM and 266.2 lb-ft of torque at 3500 RPM. We swapped out the intakes and then made another run. With the Ford original intake manifold, the car made 241 HP at 4900 RPM and 274 lb-ft of torque at 4300 RPM. So if we take a closer look at the results between the two manifolds, peak gains were solid at 19 horsepower and 8 lb-ft. More importantly, the curve gains past 3500 RPM were 25+ horsepower and 23 lb-ft of torque. The increase in horsepower and torque is because of the runner design and the larger chamber volume on the Ford original intake. Driving the car around the street, you can feel the difference past 3500 RPM with the Ford intake. And just a friendly reminder, as we can’t stress this enough, individual results will vary!


Original Ford vs. New Ford Performance

As of August 2024, Ford Performance has released a new 4.6L 2V Intake Manifold that supersedes the original Ford Performance manifold that has been off the market for years. In the interim, the only available option was the Dorman, which was more of a replacement service part than a performance part, so 2V Mustang owners were left with choosing between a power-reducing manifold or having to find a second-hand original Ford Performance intake manifold.

With the new Ford Performance intake now available, many wanted to know what the differences were and if any previous issues had been resolved with the redesign. At first glance, the new manifold looks more like the Dorman variant than the original, leaving many to believe they would see the same power losses as they did from the Dorman intake. While performance is always going to be the first question, it is important to look at how this manifold helps to solve other issues as well.

For starters, this intake is Made In The USA and definitely shows of the quality that Ford Performance is known for. An aluminum crossover is a given as all aftermarket 4.6L 2V intake manifolds solve the previous 99-00 issue of broken plastic coolant crossovers. This intake also features individual gaskets on the runners similar to the Dorman, but a drastic change from the singular gaskets found on the original PI intake manifold. The heater hose attachment port is also made of a different material to help with longevity.


Dyno Comparison Numbers

So now that we have looked at the difference between the Ford Orignal PI intake manifold vs the Dorman, it's time to see how the original stacks up against the new Ford Performance. In order for us to keep things as similar as possible, we dyno'ed the same 2004 Mustang GT with no changes in modifications. First, we ran it with the Original Ford manifold and then we installed the new Ford Performance intake manifold and ran it as well. The temperatures in the shop did not fluctuate enough to make a difference between runs and nothing else was changed between the two runs.


Dyno Technical Data

  • Cold Air Intake
  • Off-Road Mid-Pipe
  • Borla Mufflers
  • Aluminum Driveshaft
  • 3.73 Gears
  • 18x10 Inch SVE Saleen Wheels
  • 285/35/18 Tires
  • SCT Strategy Tune For 93 octane Fuel
  • The Transmission Is 5-Speed TR3650, And The Pull Was Made In 4th Gear


Looking at the differences between the Original Ford intake manifold and the new Ford Performance intake manifold, you can see that the new manifold pretty much splits the difference between the OE and Dorman.

OE Manifold
  • Horsepower: 244.0
  • Torque: 275.4
New Manifold
  • Horsepower: 233.6 
  • Torque: 264.1
Dorman Manifold
  • Horsepower: 222.4
  • Torque: 266.2

Conclusion

So, now that we have all three manifold tested, which one is best for you? Well, the answer is not as cut and dry as most would expect as there are several different scenarios to take into consideration. To make this easy, let's look at a pros and cons list of each.

Ford Original Manifold

Pros:
 - Makes The Most Power
Cons:
 - Not Available In Aftermarket (Have To Buy Secondhand)

New Ford Performance Manifold

Pros:
 - Makes More Power Than Dorman Manifold
 - Readily Available In Aftermarket
Cons:
 - Makes Less Horsepower Than Ford Original Manifold

Dorman Manifold

Pros:
 - Most Cost-Effective Option
 - Similar Fitment To Other Options
Cons:
 - Makes Least Amount Of Power

About the Video

NEW Ford Performance 4.6L 2V PI Intake Manifold (M-9424-P46A) - Dyno Runs & A Closer Look

Check out our YouTube channel for even more tech tips, installation videos, how-tos, and more. The best place to go for anything Mustang related!

Published on 2024-08-05
In this video, Landan takes a closer at the new Ford Performance 4.6L 2V PI intake manifold. We also dive a little deeper with dyno runs of the new intake, the old intake, and the Dorman intake.
Thumbnail image of the author of this article, Jay Walling.

About the Author

Jay has written content for Late Model Restoration for over 10 years, producing over 120 articles. Jay has an extensive 25-plus-year background in automotive and is a certified Ford Technician. Read more...