Sounds like a vacuum leak... Check the pcv lines for cracking (pull the
dipstick when it idles, does the car stall) specially the t at the top of the
valve cover (pull it off and look carefully).... Also check the intercooler
to t-body hose, pull it check the bottom for cracks. Any airleak into the
airflap to t-body connection will make the car stall. Try the obvious, then
you may want to make sure the closed throttle position switch is working
properly, and the duty cycle at closed throttle is at 50%....
87 5ktqRS2 320hp