i herd alot of people saying that it might mess up your gas milleage but then others say they improve gas mileage. what will putting a muffler on do except noise?

 

some show power gains. MRT shows the biggest gains so far if im not mistaken its around 10rwhp? My milage stayed about the same.

 

The upgraded muffler gets rid of the exhaust better so it gives better flow. It also improves your mpg slightly maybe 1-2 not sure but like alot of people do, they put they new muffler on love the sound and just floor it everywhere lol so then it will go down...But driving normail it will show small mpg gains.