Well basically the GTI started with the k-jet injection, then got the digifant system, and there was the 16v. The basic equipment stayed the same throughout the model history. The later 16vs got 256mm brakes, bigger servo, a roof aerial and half tint rear clusters, as did the very last run-out 8vs.
Leccy windows, PAS and all the other 'toys' were always optional extras except on limited edition or run out models which generally got alot of toys thrown in.