I replaced my injectors and ECM in my 89 gta 5.7tpi, before i replaced them the car would not hesitate and responded well to throttle...when it was running correctly. After replaceing them when its cold it struggles to maintain idle and sometimes will stall, When u drive it cold the hesitation is worst starting from a stop. When the car warms up the hesitation is still there but not as bad. I Used 21lb injectors when i replaced them and was told the stock ones were 22lb...would that be the cause?? do i need to adjust the timing again using different size injectors?. Could it be something i didnt put back together correctly, even tho i took my time and made sure everything was back. Before all of the problems the car could get sideways into second now with the hesitation it wont even spin the tires, the power is still there once you get moving. Any help would be greatly appriciated.

 

Try swapping the original ECM back in to see if the problem is the new injectors.