Here's an interesting thought. Stillen makes a CARB and Nissan approved supercharger for the Z that when coupled with their exhaust system puts out a claimed 390HP.

That's using an unmodified Z engine with stock internals that a Nissan dealer will install and Stillen warranties for 3/36.

All of those "what would it take to supercharge my '05 X ? " questions

The answer could be : $5,000 and a trip to your Nissan dealer and you can have a 350+ HP X.