The Audi RS4 is a hooligan in a European suit. It has a high revving powerful V8, all-wheel drive, but for some reason Audi made the exhaust note quite tame. For what it is the RS4 doesn’t have the sound it should.
The GMG WC (World Challenge, after their SPEED World Challenge Racing Team) gives the RS4 a proper growl at idle and an ample roar at wide open throttle. It’s also 20lbs lighter than stock so the benefits extend beyond audible.
Check out the sound in this youtube vid: