had a muffler swap done. took it back because it sounded bad and ran bad. BGM blamed everything from the muffler to a fuel problem. keep in mind this is a brand new truck. Took it to the dealership they told me nothing wrong except the exhaust. took it to another exhaust shop and they said the way they cut the exhaust right after the muffler causes reverb right below the bed of the truck. explains the awful drone. they also contributed the power loss at low rpm to how they clamped on the muffler and ran a dump right after. they said it needs to have a few turns in the pipe after the exhaust. they fied it properly but cost me money of course. take it to norman and get it done right. AVOID these guys!!!!!