Hi all. New to the forums, but I like what I see so far.
Wish I had found this place for all of my previous problems...

Anyway, Ive got a 1988 Grand Am, 2.0L Turbo. 123K miles. My daily back and forth to work car.
All of the sudden it started to idle really rough like its running on 3 cylinders. And it sounds really bad through the exhaust.
And its not all the time.
I can start it up in the morning, and it runs fine, I drive it for 30 minutes at highway speeds 60-65 mph, and come to a stop light, and its idling rough. Light turns green, I go a few blocks, and its fine.
Somedays it may only do it once or twice, others not at all.
Sometimes I start it up and it runs rough, and after the highway driving its fine.

New fuel pump, fuel filter, plugs, and wires in the last 8 months.
PCV looks good, and rattles when shaken.
Fuel injectors sound OK (the old trick of using a long handled screwdriver, and I can hear them clicking).

Could it be something electronic with the computer module?
A plugged catalytic convertor?
EGR valve?

I running out of ideas, and any help would be greatly appreciated.
Thanks

try cleaning the IAC and the EGR of and out, clean off carbon

very common issue with bad idle

good luck