'90 Camaro Running Problems

I have a 1990 RS Camaro with a 3.1? V-6 EFI, automatic trans. The problem I am having is when you start it up it runs fine but when ever you push the gas pedal it stumbles and wants to stall, but when you let go of the pedal it starts to run fine again. I have had the fuel injectors cleaned and tested, they are fine. I replaced the throttle positioning sensor (no luck), tested the fuel pressure (Good pressure), Idle control sensor (no luck), and adjusted the timeing. I was thinking of replacing the O2 sensor next. I am not getting any "Check Engine" light so I can't run any diagnosis on it for that. What else can I do???? Please help......

Replace the coolant temp sensor (about $7), had the same problem on a TPI F bird, temp sensor was the cause..temp sensor, not the sender for the gauge.

Cool... I will give it a try. I will let you know if this fixes it or not....