I had Meineke put on my Flowmaster catback exhaust (Aluminized) on my car about 2 weeks ago. It starting to backfire when i downshift and deaccelerate and it also makes this noise that sounds like the tires are rubbing. I went in and they put a resonator in to stop the backfiring and they said that they moved some of the piping to stop the rubbing noise, which was the problem. The noises stopped for a day, and now they are acting up again. I'm starting to get so pissed having to go back to Meineke and get these kinks worked out. What should I do?