APR's dyno is a dynapak, which connects directly to the car's hubs with adapters. There are no wheels or tires on the car, only a pod at each of the drive wheels, in this case, 4. This lowers the drivetrain loss, you cannot use 20% for a quattro car in this instance. The S4 does make a solid 375 hp.
'15 AW/SO F80 M3 6MT: IND cosmetic package, Gloss black grill surrounds, Macht schnell 15mm spacers all around, 3M crystalline
07 997 TT 6MT, Arctic Silver/Sea Blue: AWE exhaust, Cobb stage 2, GT2RS ICs, H&R, 19" BBS CH-R in widebody fitment