I have a 06 mini S. And I would perfer in the future to run a air/water setup and there is a few places that offer good product, air/water is expensive, but worth it... You may be able to piece together a setup cheper by using random parts used like... Subaru air/water ic (on older legacys), Bosch water pump from a S/C cobra, and some type of slim heat exchanger.... Curious, how much power are you plaining to have? 6 psi on the S is like 168ish. I would almost suggest buying a factory s/c setup and save your self alot of time, money and agravation. I only plan to run a 17% reducer pulley,Alta intake,stage colder plugs in the near future. You might want to look at
www.northamericanmotoring.com. I find all kind of good stuff for minis in there often.