What's so good about the 33 system?
Exhaust manifolds, aftermarket dumps and front popes are common between all 3 ( except for the O2 sensor bung sizes in the 32 and EGT temp probe in the V Spec and above versions of the 34). It's common knowledge that a 33 GTR cat back will bolt into a 34 with a few minor hanger changes and a bee's dick shorter.
So, where does this magical 30 HP come from?
Wouldn't it also depend if it was a 300 HP car or a 1300 HP car?