My headers and Y-pipe are on, and I'm experiencing a couple of things I don't think are right.

At idle there's an occasional pop, there's also a "tinny" noise at idle, and the car seems to not accelerate smoothly at lower RPMs, almost like it's surging, although the tach doesn't jump.

A friend thinks it's because I don't have AIR and EGR restrictor plates, but I don't think they could cause those symptoms. Any ideas?