I had a problem with my 1990 mustang at any cruising speed above 2000 rpm could not hold throttle still with out the motor bucking along, was fine at idle and while accelerating ,, mechanic friend stopped by said EGR was bad, disconnected vacuum from EGR and plugged vac line,, took for a ride and bucking stopped,, very nice in all gears even at low rpm in 5th gear.. now im getting a horrible whistle at idle. reconnected vac hose to EGR and noise stopped, of course I dont want to go back to 1st problem of bad EGR so I made a plate to fit under EGR in an attempt block off. now I have same whistle noise and check engine light. The motor has Trick Flow street burner heads and intake kit, F303 cam smog pump and cats are gone , 70 mm thottle body and BBK cold air intake, so how does this EGR work with the ports on upper and lower intake, will this EGR spacer delete stop these problems, will it work with my BBK cold air as the EGR is thicker than the delete bracket and I see a make up problem just looking at the plumbing of it all.. btw I am a plumber by trade ,, Thanks
I think you have something else at play. A whistle at idle is typically caused by either the air passing the throttle blade, a small vacuum leak, or the PCV system not being plumbed correctly.
Connecting the vacuum line to the EGR should not have made any impact at all at idle as vacuum isn't applied to open the valve until a cruise condition is met. Unless the cap you used to plug the line when it was removed was not completely sealed, creating a small vacuum leak.
The PCV system should be a closed loop system, no open-air valve cover breathers. These allow unmetered air in to the intake and will cause a lean condition. In the back if the lower intake manifold, the mesh filter should be installed followed by the PCV grommet. Then the PCV valve and a vacuum hose attaching it to the upper intake. This comprises the suction side. On the supply side, you should have a vacuum hose running from the throttle body to the valve cover filler neck. A sealed oil filler cap should be installed on the filler neck.
To set the idle speed/throttle blade position, get the car to normal operating temperature. Shut the car off and unplug the IAC motor. Unplug the Spout connector. Start the car and mechanically adjust the throttle stop screw until you achieve an idle speed of 600-700 rpm. Shut the car off an reconnect the IAC and the spout. Start the car and let it sit at idle for at least two minutes. After that, turn on the A/C and allow it to idle another two minutes. Take the car on a 10 mile drive with plenty of stop and go situations. This will allow the PCM to relearn idle speed and spark advance for idle.
Running this delete plate with the BBK would not be an issue. The elbow tube that passes through the apron is not fixed to the trim plate so it can move. If you are running the mounting bracket underneath the MAF, it will need to be modified or removed.
the whistling is coming from the throttle body itself, BBK throttle bodies and mainly the 70 millimeters are notorious for a whistle at about half throttle, it does not affect performance in any way except for just you hearing the whistle, so no need to fear it's just the throttle body, not really sure why, but hundreds of people have had the same issue including myself, I ditched the BBK 70 and went with an Accufab 75 millimeter