330 exhaust has two pipes coming out, one of which has a flap that opens and closes. this might be the problem?
there is a vacuum line that runs to that pipe(it the one on the right on my 330) check to make sure thats still attached. the line is under the bumper abov the pipe right after the muffler.
otherwise $135 doesnt seem too bad for a dealership repair.
but i would check that vacuum line.
otherwise i would check out E46 fanatics, they have a lot of information on E46 models..just search and see what you come up with.
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