Better air intake - A lot of folk seem to take the intake pipe from a PD160 (i think), not done it myself and looking down another route.
No need for the PD160 intake of fitting an open cone filter.
As MrNorma said, need to
help the engine breath better (so air in and exhaust gases out) So:
Open cone filter + Forge TIP
Milltek turbo-back exhaust with high-flow cat.
Forge intercooler pipework (Forge do replacement intercooler pipework for the restrictive OEM stuff. With a
Cupra model, you only need one pipe that sits on top of the crash bar and goes from intercooler to the throttle body/intake manifold)
Then get your car mapped to suit the mods. This will take you to stage 2... happy days!