1987-93 Mustang Holley Terminator X Fox Body MPFI Kit by Holley

Price: 1401.95 USD
Availability: InStock

1987-93 Mustang Holley Terminator X Fox Body MPFI Kit

The OG is back! Fox Body Mustang Holley Terminator X Kit - Overview & Full Explanation (550-937F)

Transform the efficiency of your 1987-1993 Fox Body's Mustang's power plant with the help of Holley's Terminator X MPFI management kit!

Item #HLY-550937F
MPN# 550-937F

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LMR showroom & will call pickup service will be closed beginning Monday 9/21/26 for renovations until further notice. Need help? Contact Us.

Benefits

Real-Time Self-Learning Fuel Strategies
Built-In Boost & Nitrous Control
Plug & Play Harnesses
On-Board Diagnostics

Features

Pre-Loaded With Base Maps
High Impedance Injector Drivers
Customizable Gauge Display
Built-In 1 Bar MAP Sensor

What's in the Box

(1) Terminator X ECU
(1) 3.5" Touchscreen LCD Handheld
(1) ECU Mounting Bracket
(1) TFI Ignition Adapter
(1) Primary Engine Harness
(1) EV1 Injector Harness
(1) Bosch LSU 4.9 Wideband Oxygen Sensor
(1) Built-In 1 Bar Manifold Absolute Pressure Sensor
(1) Manifold Air Temperature Sensor
(1) Vacuum Hose Adapters

Holley Terminator X EFI Kit
Take control of your 1987-1993 Fox Body Mustang 5.0 and transform the power, efficiency, and drivability with Holley's Terminator X EFI Kit! Don't settle for a factory ECU with a cumbersome tuning interface or pre-programmed tuning chip when you can have complete control of your engine, self-learning fuel strategies, and the proven, race-winning technology of Holley's EFI at a budget-friendly price! The Terminator X features real-time fuel learn, high impedance injector drivers, an integrated 1 bar MAP sensor, and 4 programmable inputs and outputs. The inputs and outputs are ideal for electric fans, boost control solenoids, progressive nitrous control, and much more. The Terminator X comes fully loaded with base maps for common V8 engine combinations to get you out of the garage and on the road/track fast! The 3.5" touchscreen LCD handheld contains an easy-to-use calibration wizard as well as tuning and gauge display functions. Holley EFI's industry-leading, easy-to-use software is provided to allow full laptop access to advanced tuning. Whether you are building a budget beater or a boosted race car, Holley EFI's Terminator X has the features and technology you need at a price that won't break the bank!

Product Highlights

The harness included in this kit was meticulously measured to be routed through the firewall, imitating the factory wiring harness.
This is a NO LAPTOP REQUIRED kit! Simply enter the information about your specific engine combination into the wizard on the 3.5" handheld touchscreen and the ECU will build a tune map around your specifications the more the car is driven! No need to be an EFI or tuning expert!
Bolt-On Multi-Port Fuel Injection system

Full List of Features

Fox Body Specific Engine Harness
High Impedance Injector Drivers will safely power most stock injectors and Holley EFI Injectors. Injector support chart provided in the instructions (Will NOT control Low Impedance Injectors).
This Terminator X system utilizes the Bosch LSU 4.9 wideband to relay AFR information to the ECU for accurate reading and precise tuning control.
Featuring a built-in 1 bar MAP Sensor, this kit includes vacuum hose adapters (1/8th – ¼ and 3/16ths).
For Boosted applications, you can disable the internal MAP sensor, and utilize an external MAP Sensor for more accuracy.
Plug and play ignition capability with Dual Sync and HyperSpark Distributors, adapter part #558-323 required for HyperSpark Distributors.
4 Inputs – 12v, Ground, 5v, and Frequency, for things such as additional pressure sensors, or activation triggers for nitrous activation, or a trans brake.
Boost Control – Boost vs Time, Boost vs Gear, Boost vs RPM, Boost vs Speed, Boost Safeties.
Nitrous Control – Single Channel of Wet or Dry, Progressive or Non-Progressive, Rich/Lean Safeties, and target Closed Loop AFR.
Advanced Tables – 4x 1D Tables, 1x 1D per Gear Table, 4x 2D Tables, 1x 2D per Gear Table, can be used for any custom tables you can dream up, such as Flex Fuel Sensor Offset Table, or a custom fuel or oil pressure safety!
On-Board Diagnostic LEDS for ECU Power – Engine Run – Wideband Status – TPS Calibration – Crank Signal –Cam Signal. This allows you to identify any Critical engine issues at a glance.
The included 3.5" Touchscreen Handheld contains a calibration wizard, that allows you to quickly build a base tune for any domestic V8 engine. Additionally, the handheld provides internal data-logging and a fully customizable gauge display.
Plug and play compatible with more Holley EFI accessories such as; analog-style gauges, shift lights, various modules, 12.3" digital dash support!
Includes Holley Sensors 534-10 (Temperature Sensor) and 543-20 (Intake Air Temperature Sensor)

Tuning & Software Note

Holley provides the Terminator X Tuning Software for free to completely control your power plant!
The Tuning Software Lists Injector Data For Varying Applications.

Suggested Parts

This product is intended for off-road use only. Off-Road Disclaimer

Holley Warranty - Click Here

Ford Mustang - 1987, 1988, 1989, 1990, 1991, 1992, 1993

Fitment Notice

Fits 1987-1993 Mustang EFI 5.0/5.8
Will fit 1994 and 1995 5.0 Mustangs with a manual transmission if used with a 1987-1993 5.0 distributor.
Will fit 1979-1986 Mustangs, but this kit will not be as plug-and-play for these year models. Neither LMR or Holley have the wiring colors or install instructions for these year models so custom installation will be necessary.
The terminator replaces the OEM engine wiring harness and ECU wiring harness. Something to note is the air conditioner clutch cycling switch connection is on this harness. The air conditioning will need to be custom-wired to correctly operate.
Does not include EGR connections.
Due to the custom nature of this product, please be sure to read all installation manuals provided.
Terminator X ECU's are designed to be mounted with the LED's facing up.
When paired with a Digital Dash in the stock gauge bezel, you will need Holley's CAN adapter part #558-425.

Transmission Fitment

This will work with the following non-electronically controlled transmissions:

AOD, T5, TKO, TKX, T56, SROD, C4 & Powerglide

This will not work with electronically controlled transmissions:

AOD-E, 4R70W/4R75W/4R100, 6R80/10R80 or 5R55

The OG is back! Fox Body Mustang Holley Terminator X Kit - Overview & Full Explanation (550-937F)

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!

Harness Manual

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Wiring Guide

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Fox Body Holley Terminator X Installation Instructions

Published 4/30/26
Holley Terminator X vs Terminator X Max

Published 9/19/25

California Residents:

WARNING: Cancer and Reproductive Harm- www.P65Warnings.ca.gov

About This Brand

Holley, The Heart & Soul of Performance.

For over 100 years Holley has been proven to be an industry leader by providing Mustang enthusiasts and racers with the high performance carburetors , intake manifolds, cylinder heads, and other quality performance components needed for today's competition. Holley's performance Mustang parts are perfect for any daily driven or high horsepower race car.