Finally got back to RENNtech to have them dyno my RENNtech stage 2 C63 AMG. They were even nice enough to flash it back to stock for baseline dyno numbers and then reflash it again to the stage 2 ecu flash. The temp was ~ 92 degrees F / ~ 68% R.H. and they had 1 large fan blowing toward the engine. Anyway, here are the numbers with dyno attached...
C63 AMG Stock baseline: 366.82WHP / 353.83 lb.-ft. RWTQ
C63 AMG RENNtech stage 2 ecu flash: 411.82WHP (+45WHP) / 368.29 lb.-ft. RWTQ (+14.46 lb.-ft. RWTQ) 
Assuming 20% drivetrain loss, then it would mean:
C63 AMG Stock baseline: 459HP / 442 lb.-ft. RWTQ (fairly close to MB's advertised 451HP / 443 lb.-ft. TQ )
C63 AMG RENNtech stage 2 ecu flash: 515HP / 460 lb.-ft. RWTQ!!!!! 
So far, I've been
very happy with my RENNtech C63 AMG!!!
