yea i heard that the res has to stay on, i actually took it off, cuz it had a hole in it, and i just had a new cat put on, and found a couple of leaks, that's why i'm looking at headers and exhaust. the resonator def has to be put back on. i like a nice tone to exhausts, not a tin sound. is the magnaflows really loud? or a nice/or no tone at idle?