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.

 

try reposting this or asking someone in the DIY PROM or DFI and ECM sections u may have better luck there