If you read the interviews with Novitec, their R&D guys 1st tried to do a Twin Turbo kit for the 360 and decided it was not the way to go. Apparently there was problems with massive heat build up!
In the end the perfect solution was to use two small centrifugal superchargers instead of 1 big one, this not only improved cooling (superchargers emit much less heat) but also the relatively consistent power increase didn't place as much strain on powertrain or engine as turbo's kicking in.
This also gave a very nice solution because the engine also didn't need to be rebuilt with lower compression ratio pistons. In fact they didn't need to 'open up' the engine at all (!), all they did was use relatively low pressure's and yet they still achieved 25%+ power increases over stock, one spec is 555hp and the other is 608hp!
Parts used; (spec 1, 555hp)
1. exhaust: race exhaust, cats (or test pipes for offroad)
2. fueling: fuel rail, injectors, pump & add-on ecu
3. supercharger: twin small centrifugal superchargers + water coolers
(spec 2, 608hp)
1. carbon fibre air intake
2. exhaust heat shield
Read all about it on the Novitec website, the interviews from magazines are the most technically revealing, even describing the superchargers used, etc.