The 2003 SVT Cobra I had seems pretty tame, by comparison. The supercharged DOHC on that model was rated at 390HP, but dyno testing by owners confirmed it was more like 425HP.
They usually made way over 350HP at the wheels, stock.
Getting rid of the junk IRS on those and going back to a live axle in 2005 was a brilliant move by Ford to please the muscle car crowd. Muscle cars are supposed to rule at the dragstrip, not the autocross track.
Theoretically, that should be true, but look at post #19. The BOSS is live axle and is destroying everything - even on the most winding tracks like Laguna Seca.
Really IRS good for a more responsive/smoother ride on a bumpy road, but on smoother tracks it doesn't make much difference. With the right suspension tweaks (which Ford Racing has done with the BOSS) a live axle perfectly suited for track use.