ok... start by memorising the location of this thread
http://www.golfgtiforum.co.uk/index.php?topic=62370.0theres loads of guides and ideas in there for you
then from there i suggest if you want to mod your 8v you look into the following
get a cam from an early mk2 8v gti, its like running a 260 degree cam and with a standard head a lot of aftermarket cams above 260 degrees dont give you their full potentional as the head chokes at high rev
Look at a decat, if you want to do this cheap then get a cat from the scrappy and hone it out with a crowbar to remove all the cat insides... cheap and effective
a chip can be sourced from ebay from a seller called powerchips, they are 30 quid and well worth the money (fitting guides in the above thread)
Deramp your throttle body and port match it to your inlet, making the air flow better
Drill your airbox as per the guide in the above thread
BRAKES!!! the better brakes you have the longer you can stay on the accelarator.
thats about all id suggest you bother doing with your 8v unless you start looking at porting a head yourself... get a spare head and see what you can do.