If you know someone who works for VAG or go to a stealer that does a good discount for whatever reason (forums etc), you will get an S3 intercooler for just under £300. They are fitted reasonably easily, but I believe that garages who have done a few can do it in 2 hours now, same as we did after our 2nd one.
2 hours at garage rate may be £100.
Milltek is gonna cost about £1k, but you may get another brand for less by now as a few companies have their model available too.
The S3 intercooler drops inlet temps by approx 20%, and gives a couple psi more boost on spool than with the OEM intercooler.
Edit: If you get a garage to do it, make sure they have done a few already as you learn a lot from the first one. Things like the screws/bolts for the ends of the core are different and you should have these available before you start. Knowing where all the screws that hold the bumper on is another thing, and getting the core pipes clipped on properly is fiddly too. Our first one took 5 hours including sourcing bolts, and the 2nd one 2 hours.
