Down pipe off a TT, LCR or S3 will not fit the Ibiza, you will need to get one made up = £££

Engine internals are good for 330-350bhp before you need rods.
 
Could you use a downpipe off a tt as the main bit and get a fabricator to weld onto it if to small or bend it in the right direction etc
 
Which TT are you referring to?
As there is also the 1.8Turbo TT, and downpipe off that is same as Golf (k03s) and therefore fits our cars as standard (I have one from US). This will therefore not fit the k04.

Have a look see on here for people who have k04 installed and see what DP's they used. Think they indeed had them made, same as manifold.
 
Well dont the tt or s3 manifold fit standard onto the cupra so it will only be the downpipe i need