Just wondering why my car almost always ( 3 out of 5 times) backfires when i run it hard from first to second gear..... i usually shift around 5500 and i get a backfire and ive been told i shoot some flames from my exhaust. I run Sunoco regular fuel.. whatever octane that is (89 i think)......my car has 60k on it.... not having cats probally doesnt help but can anyone tell me exactly why this happens and if its something to be concerned about.