i put a ls1 out of a 98 corvette. i got it from a guy that had it in a 57 Chevy. it came with a stand alone harness and the original comp. when i start it it runs for a couple seconds and shuts down. im getting a code for anti theft. the guy before must have had the vats bypassed some how and was wondering what i have to do to fix this problem im stumped and any help will be good.