The chassis is the best part of the the GTI, thats why you dont see many of that type of mod about for it. There is also one that goes in the boot across the rear strut housing but from what people have said on here, the GTi just doesn't need them. You need to be going down the route of taking weight off. S3 hubs and lower arms, lighter brakes and wheels, back seat out, air-con removed. then great suspension and arbs.