recently i bought the old full-race.com coupe and got it retuned by charm city tuning and everything was
good for a week but now it wont stay running.

problems:
wont stay running
mil will flash really fast at 1700rpms
300 wont pick up the mil
car loads up and starts to backfire

everything was fine. i did a full pass and drove home and parked it then next day it started running funny.
i had some harness problems when i got it and a tps problem but thought i fixed it and a few people seem
to think its the harness is grounding out or the engine grounds or even the tps again but it was reading
when i logged it



help please.