brakes on a pre 89 mk2 16v use the same as the 8v gti, after that the discs/calipers are bigger/uprated and also has a bigger master cylinder.
The inlet manifolds changed around the 88' mark, originally they were 45mm ports, then they changed to 50mm, not sure what the gains were but im sure vw didnt do it for nothing!!
PAS was an option, as was Air Con at one point, ive seen old small bumper 16v's with out leccy windows so wether they were and option or the ones ive seen with had them removed for weight!! lol
i cant think of owt else.
oh yeah early ones had normal back lights none of the half smoked stuff goin on!! lol

id just like to add........
guess whos just got himself a 3dr 89 oak green valver...........
