Exhausts/mufflers are only good for getting the sound you want & do almost nothing for WHP. If you are looking for power outside of a tune add downpipes but again a dealer will not be happy with you. Downpipes are most effective if you have a tune.
Best bang for the buck ($500) is the JB4 piggy back tune. Cobb is also a good tune, but more expensive.
My car with only a JB4 & FMIC about $1100 does 12.5 X 114.5
Vbox is from a FBO JB4 car that runs 11.1 X 130 at the track.
2013 BMW 135is 6spd conv - 2011 BMW 335is Coupe JB4/ISO
2010 BMW X3 - 2009 Ford Expedition 4X4 EL - 2009 V-Star
2003 Nissan Xterra 4X4 - 1998 Ford Ranger 4X4 Splash
Last edited by bear-avhistory; 12-25-2012 at 10:44 AM.