Nice one Cerec1, hope you're enjoying it! Big drop in power though? I'd thoroughly recommend fitting a pedal box, it really sharpens up the throttle response making the car feel more alive and eager. I also fitted a short shifter to mine which really improves the feel of the gear change. Very easy mod, nice and cheap too plus it was a genuine VW/Audi part (apparently it was an option on the TT) so it keeps it oem. About £46 from an Audi main dealer iirc. Otherwise I'd recommend Michelin PS4/S tyres (depending on wheel size), big difference with grip, noise and comfort!
If you haven't already, have a look over at the model specific section, pretty much everything you can think to ask has probably been covered before with the full range of expected replies (helpful, informative, irrelevant, funny, sarcastic.....)
http://www.golfgtiforum.co.uk/index.php?board=117.0And welcome to the forum!