Hey, i my car is kinda backfiering now, it will pop like every 5 senconds and he can see the engine lean foward when it pops, but it isnt a loud pop. I wonder whats causeing this. I think it might be a bad fuel filter and clug injectors. And my katback is kinda lose, i was trying to put my test pipe on and the bolt on my kat rounded off when i was trying to take it off, so no i cant tighten it or take it out, so im stuck with an exhaust leak until i find a way to take that bolt off and put a new one in. And i was think it might be my exhaust leak causing my car to make backfiring thingy. What do u guys think, oh and this started happening when i retarded my timing, change my spark plugs to cold ones, and shooting the nitrous.