I own a C6 rs6
Love the car
Bought as a project with known faults
Unit 20 pulled engine and sorted out all the common issues like pump module leak
Coolant pipes in wing
New intercooler
And fitted a miltek non res for me
Run for a while like this then
Mrc secondary cat pipes and engine and gearbox maps stage 2
End result was 742 ponies and 1039nm torque according to dugs dyno
Had it for 3 yrs now
And that's me