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.
09 E92 335 M tech 6MT, Titanium Gunmetal Alufelgen SF 71s, Helix FMIC, JB4
2010 GT-R, bolt-ons: 10.72 @ 132 so far
Deposit placed on F80 M3