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.
'13 Black Sapphire Metallic 335is DCT, BMS CP/DCI, MHD stage 2+ 95 octane, Wagner Evo 2
'14 991 GT3, Sapphire Blue / Black, 11.30 @ 124
'07 997TT 6MT, Arctic Silver/Sea Blue: FBO E85, stock turbos: 5.9 60-130 (now with 656 whp, 700 wtq)
Prev: 2 FBO 335 6MT, and '15 F80 M3 6MT