I have a 2010 Cobalt N/A. I've put in a Cold Air Intake, and full 2.5" exhaust. In every gear when I accelerate, the exhaust gets really loud after 3000 rpm, and kinda sounds like it rattles but it's not. I have no idea what this could be. There is nothing loose all good, it is a Flowmaster cannon style muffler, I do not know the exact model number.
Probably doesn't have a resonator like OEM. These are designed to cut loud frequencies at cruising speed.
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