I would trust Scott Fisher about specs at Vegas (wish I could afford to go to the Paris race this year) and most other places. We don't shim our motors up in Colorado Springs due to the lack of air, but when the guys go down to the Paris race they do as a precaution (couple of our guys have popped plugs in Vegas because of not shimming). You could try it with stock shims and go from there. Changing plugs can do the same thing, it's just advancing or retarding the timing of the engine.

I'm using the VR12 pipe right now with the Mugen X12. You'll be happy with it. Better than the RD logics Turbo II.