Sounds about right. I dynoed my M3 at Carbconn back in 2009 when I lived in Seattle. Stock with just Eisenmann muffler and drop in filter it put I believe 338whp and then with aftermarket Fabspeed high flow cats, Eisenmann, and filter it put down 362whp from what I remember. Definitely impressive numbers for the 1M!
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| Satin black badges
2015 BMW X5 35d|Mineral White| Mocha
2017 BMW M3 ZCP| Mineral Grey