I recently gutted my cat, and about a few days later, I was starting up my car and whenever I would let off the gas it would backfire bad and crackle all the way till it got to idle, and it still does today. I have flowmaster muffler and gutted cat, thats all the exhaust mods ive done. Could this be my gay stock exhaust or is it a spark plug?

 

nm, i saw the previous topic on it heh