VXR/OPC Corsa's are not that fast at all.
i raced one in ciney with my full stock GTI and i still nailed it... specially off the line they are slower because of their gearbox ratio's wich are to short.
so they can't get traction down verry well... they are better in rolling starts, but nothing spectacular
as for the rest, i have stage II polo GTI an i did test against Golf V and VI GTI with remap.
both could not keep up with the polo, not even a bit!
tell you something, i have friends with a Leon Cupra R, remapped to 302Hp.
and the other one has a Renault Megane RS Trophy, also remapped to 297Hp and 443nM.
the cupra is equally as fast as my GTI, and i mean exaxly as fast, from rolling start 2nd gear all they way to topspeed.
from a standstill i nail him with 2-3 carlengths.
the megane trophy is a bit slower, i pull away 1 carlength on it and after that it stays the same.
only from 4th to 5th gear he comes passed for a moment, because he is allready in 5th when i'm going from 4-5.
for about 10sec it stays the same again with advantage for the megane, but then he needs to go to 6th gear and i again pass him
but the megane is faster from standstill as the cupra, it can keep up with the polo as his front bumper is at my rear bumper.
those cars are pretty good competition for a stage II GTI.
also tested against a Astra VXR with 310Hp, he also was equally as fast as the polo, on torque i have better and faster spool up so i can get a nose in front but then it stays the same, also tested from standstill up to 150-160km/u and it was the same, polo a nose in front.
i really want to test against the Focus RS, there are driving about 6-7 of them in my town and also a RS500, allways spot them on other side of the road
but i allready know what the outcome will be also

(RS500 will be a step to high on the ladder, those will be faster as me, pretty sure...)