You may have heard of the problems with the front discs on 90 20v Qs and S2s. Grunch, grunch, grunch and all over the road braking. I actually got Mintex to make me some special pads (they cost a fortune approx £120 ten years ago). As luck would have it EBC 'Green Stuff' pads came onto the market at that time and I fitted a set. The change was dramatic, and gave me full confidence in the braking of the car. Later I fitted Brembo cross drilled discs, front and rear, to give the car the brakes it deserved, and needed.
I have been driving for longer than I care to admit (I used to rally Escorts and then Saabs back in the 1960s and 1970s) and have tried all sorts of pad and disc combinations. At the moment most of my cars (Mk I GTI, Mk II GTI, 100 Avant, VR6) all utilise 'Green Stuff' combined with ATE Grooved Discs. The only car not with this combination is the 90 20v Q. This has Brembo calipers, discs and pads, front and rear (RS2 rear discs).