i have a 89 TA, I have a new prom chip for it, the car starts up fine and idles just fine for a few minutes then u give it some throttle then drop back down to idle and then it acts like it cant hold idle and stumbles and then catches, then dies, it idles right round 1000, advance timing is 29 degrees at idle, o2 is working and all my sensors are, I have no check engine light even when it dies, itll for no reason drop down to round 500 then die, timing while at 500 is 16 degrees, lean afr, I have a new msd cap, rotor, Mallory ignition module, msd coil, and I just put a new esc module in, im thinking its a electrical issue but I need someone with more experience to chim in

 

What chip? Sounds like it's getting too much fuel or not enough. Did you check fuel pressure? Ohm the injectors?