golf 18t next step in power increase

[just]

hi,i have brought just a gti 1.8 turbo which has been modified and is supposed to be chipped to 210 bhp or 180 at the wheels.Whats the next step ?,i have been offered a k04 turbo,will this fit straight on ?
Does anyone know what audi tt parts can bee used for power gains and has anyone tried any performance parts such as awsome gti's air intake pipes for the intercooler?

[Ivor Mk4 Turbo]

I don't think KO4 (S3) turbo is the way to go, from what I've read.  Too much hassle for too little gains, IIRC.  I'd consider the Jabbasport IHI conversion for £2500+, which will see you to around 350 ponies!!!