Review on Flowmaster 52573 2.5 Inch Inlet/Outlet 70 Series Muffler BBII by Robert Blanton

love it. My 2001 Ford f150 5.4 V8 with double cab lariat cabin noise is 2 out of 10 but when you are outside it sounds like a strong V8 should sound. I also immediately noticed a difference in overclocking performance. The 5.4 is an engine that doesn't get enough air, and anything that helps it breathe seems to help. While I expect the overall HP gain to be small, it's still there. If I had to do it again I'd probably reach for the 50 series Flowmaster for a little more growl, but I'm still very satisfied.