Well I took the GTA out this morning for a long test drive and watched the needle on the fuel guage drop...Something is definately wrong. I will go to a heated O2 sensor as soon as it comes in. I do have a question though. I purchased an ECM awhile back as a spare. It is a factory authorized Delco re-manufactured 01227165 ECM. It has the blue memcal under the access cover so it hasn't been pilferaged. Would you guys recommend swaping this with the one in my GTA ?

 

The best advice I can give you is to connect a scan tool(must be GM OBD1, 12 pin ALDL) and look at Block Learn and Integrator for clues to out of whack fuel correction. As far as O2 sensor brands, Bosch is the original maker of EFI and the O2 sensor. I've never had a problem with their sensors on domestic applications. Denso makes the very best O2 sensor. NGK isn't bad.