not too sure on the engine as i have a V6, but the mods i have....
millktek, exhaust system
BMC cardom air filter
Orbit ring - this goes round the gear leve and lights up, very tasteful
seat cupra front splitter
led side lights - look for h6w bulbs wide angle
as for ones nomally fitted to the turbo cars....
V6 rear valance single or double exhaust
V6 spoiler entension
v6 bumper and grilles
centre armrest
cruise control - fitted esily with audi parts
engine remap
the list is endless really depends on how much money you have and how far your willing to go.
im not supposed to advertise on here so i will send you a pm with some useful websites