I remap an awful lot of MK6 GTIs in various stages of tune. Stage 1 is usually problem free, with stage 2 torque I'd say 50% of them suffer with clutch slip. It all really depends what sort of life the clutch has had but if you drive them like a GTI is supposed to be driven, even the standard cars seem to suffer.
I think it works out around £850 to upgrade to a Sachs organic kit that works with the stock flywheel. They're rated to 407lbft of torque.
