All I have done to it is header cold air intake and catback exhaust no cat it throughs an o2 code when I put the obd2 ecu in it but it did that befor I converted to obd1 so I don't think that would have anything to do with it.It just started doing this shit I haven't been able to get out of work to get it checked out yet figure I would through it on tr and see if anyone knows what the problem is first