please help with messed up idle!!!

My friends 91 GT is having a few issues, that I am trying to fix but cant quite.

It will idle fine most the time, except right after I start, you have to play wtih the gas pedal to get it to idle...then it will idle for a couple minutes, and die. I relearned the idle, set the TPS to .95, cleaned the IAB, replaced the TPS, BUT the code reader wont work on it, it wants to die when I try to run it, and wont do anything. I tried KEOR and KOEO and the code reader wont work on either. It will work on any other car though...Its also down on power for some reason.

Any Help??

Thanks