It's sounds pretty similar to the Megan racing exhaust which is 500-600 bucks new! Check YouTube to compare. Get the Megan instead. It's lightweight too.
Not sure about the HP claim, but if its just a muffler, I doubt it.
///2013 AW 6MT E92 ZCP M3/// Black 359M Wheels/BMW Performance Carbon Fiber Spoiler and Mirror Caps/Arkym AeroSport Front Lip/Turner 15MM Spacers/LUX 8 LED Halo/IND Gloss Black Grills, Gills and M3 Emblem/30% 3M Tint/BMW Interior LED/MusicCar Subwoofer Enclosure/JL Audio 12" W6 Sub and XD600:1 Amp/Euro Sunglasses Tray/Ceramic Coated Megan Racing Exhaust/AFe Dry Air Filter/RPI Intake Scoops/Euro MDM/Feature Coded.