Depending on how serious you are, perhaps it's a good idea to start a thread in the track section.
Those boys will sort out your brakes, suspension & cage for how serious you are then start one in the MK3 board for supercharging.
But I feel your budget will take a BIG hit after the suspension, a PROPERLY installed cage and brakes.
But IMO they are far more important then engine BHP and thats purely the reason, IMO that the 16V is a far better choice for track as it's lighter already.
& as Chuff said, how are you going to see when it mists up?
I'm sure DH will offer some very to the point & sarcastic advice but I would actually listen.