I have a 1990 Firebird, Trans Am, GTA. In the last 7 years it has been going through some major changes. Generally, I have converted it from a 5.0L automatic to a 5.7L, 6-speed. The overhaul is almost complete, however, I have run into a problem with the ECU. The current ECU has an Hypertech chip installed in it. I do not know what the characteristics of this chip is as it came with the car when I bought it. Needless to say, this chip does not like the 5.7L engine at all. I can start the car but the cold idle is rough and the hot idle is rougher. I am considering replacing the existing OBD1 with an OBDII ECU which would allow me to program the parameters or even replacing the existing ECU with a stand-alone ECU. I am not sure which is the best method and was wondering if anyone can provide some background to either of these options.

 

you didn't specify what fuel system...then maybe i can help