Today I dropped my truck off and had exhaust put on. I ordered Flow 50 series HD. The part they shop recieved and installed was Flow 50 series SUV. It is quiet, not really much different than stock. It pisses me off. Anyway, how much louder is the hd over the suv? I know the graph on the flow site shows a large difference, but I am not sure how much difference there will actually be. I am taking it back tomorrow for them to order the right parts.