I just put an engine in my 87 supra and its driveable now. It runs and idles fine below 4000 rpm. As soon as i drive it and git on it around 4000 it falls on its face and starts backfiring! The cat is not cloged and the spedo cable is borken and does not work if that helps at all. It seems a little week on power with a 4 angle valve job and a turbo head. The only code i have is a code 42. Can anyone help me!:1zhelp: