On my 91 Z28 I changed from auto to T56. I sent my prom in to get it changed (while the car was apart) from auto to manual, turn the egr off, turn vats off, raise rpm/mph limits. The work was done by someone selling the service on ebay. He mailed me after he had received the chip and said that it was incoded (I knew it was an after marked chip, but he didn't ask about that before I sent it). He stated that it took alot of extra work but that he had been able to make the changes. When I reset the ecm everything works fine the first time I start the car, speedo, cruise, idle, runs great! Shut the car off, turn the key back on, start the car, and the ses lite never goes out, and I get a code 51 "prom error" I think it goes into limp home mode as the fans come on and stay on, and driveability is poor. Am I screwed? I tried to search for code 51 but the search won't take the #51. This is the only thing left for me to work out on my tranny swap, man I love the T56!! Thanks for any input!