Mk2 GTI's had 226mm discs, all non GTI's had drums.
Out of interest why do you want to stay 4x100
For a number of reasons:
To keep the cost down, so I don't have to do front and back at the same time, so I don't have to buy new alloys untill my Porsche rims are refirb'd

Lastly and most importantly, the adapters i need for my Porsche rims will later be used on my MK1 Golf project, so I need to keep the same PCD!