I would be surprised if a muffler added any power. Maybe 1 or 2 hp if you must be optimistic. Hopefully it doesn't cause any loss of power! I'm not sure if my Eisenmann Race made any difference plus or minus, but sometimes I feel that my car does not accelerate as fast ever since I installed the AFE filter.
2012 Audi R8 V10| 6MT| Suzuka Grey| Dallas Performance Stage 1.5 Twin Turbo| 817whp pump| 950whp on 109 octane| GMG springs| Klassen M52R| Toyo R888R| GT Tails| GT wing| Black Optic Grille| CF everywhere| Satin black badges
2015 BMW X5 35d|Mineral White| Mocha
2017 BMW M3 ZCP| Mineral Grey