I don't think what your care does is abnormal. When I am in high rpms my car gargles quite a bit and it sounds like backfiring but i think it's just the nature of the motors. If you're positive it's backfiring, then maybe you're running rich. Putting offroad midpipes on can cause unburned fuel to be ignited which causes the backfiring. I also don't know why everyone is making fun of you, although your spelling wasn't that great.