I think that for really high power applications,your biggest problem is going to be the integrated head/exhaust manifold,as that will restrict things at some point.
Of course,as has already been said,there are hybrids such as the TTE and so on,and APR will release a bolt on kit based on a Borg-Warner turbo soon,but most these are unlikely to go much beyond 500bhp.
The best way forward for anyone thinking of this sort of thing is to decide first of all how much power is going to be enough,and then begin to plan from there,as it's very easy to waste money on projects like this.
Software of course is very important,and I would say that a WMI kit would also be very useful,but those are easy to fit and map.
This is easy to say,but unless VAG have significantly uprated the internals of the new engine,the safe limits for the internals would likely be around 440-450lbs.
It will be torque that kills the engine,not bhp.
