....
Personally I don't know the answer to that question but if you're running about 280 bhp on the FWD GTI, regardless of K03 or K04, then I would strongly advise that a Quaife ATB diff would be a good mod so that you can better deliver that power onto the road. Or are you simply after "gains", i.e. high numbers?
Each to their own of course, but power is useless if you can't get it down onto the road. (in my opinion)