2005 Grand Prix: On a cold start my engine will start strong and loud. Warm start: it starts off with a weak idle and often dies immediately if i don't give it a pinch of gas ( i use 'pinch' because it doesn't take much, just a tap).
Use 89 ethanol blend. Seem to get a stronger start when i use some kind of octane booster/injector cleaner. but every mechanic I've talked to says I shouldn't need to do that.
One theory that has been brought up is because of the exhaust system changes i made. Took off the resonator and turned it into a cat back dual exhaust made the sensor (???? forgot which one) go haywire because of the exhaust pressure difference(?) (not mechanically inclined, so i don't remember the full details of the conversation).
Was hoping someone here might have any ideas on why it happens or if the theory above is right.
