Driving around today, started hearing a rattle. Isolated the rattle to 1900 & 2500 RPM, not dependent on gear, acceleration, etc. Got home looked over entire exhaust, looking for lose bolts/heat shields everything nice and tight (I check this stuff spring and fall). Basically isolated it to the muffler, and can stop the rattle with a hand on the exhaust tips. Mufflers are 2.5 years old. This crap irritates the hell out of me. I guess I'll spend the day tomorrow removing the F'n bumper and muffler to see if I can find the exact crack location. Just a data point out there for those looking into aftermarket exhaust.