I can answer that.

The rest of the drivetrain for the Xterra has one weak link. The CV joint on the rear drive shaft. That little baby is going to cause some havoc with too much power and a sticky situation.

Another thing to remember here is that the VQ40 is a stroked VQ35. Like a making a Chevy 383 out of a 350 (by putting in the crank of a 400, but that's another thread). The bore is identical, but the stroke of the crank is different. The pistons are also different, probably not as strong as they are clearanced for the long throw.

So in short, unless you could restrict yourself to below hmmmm.........say..5psi(?), then I don't think the engine would take the abuse you're talking about.

I could see a 4psi boost with good reliability. But I'll wait to see what comes around for the engine before I go ordering too many go fast parts.

By the way, the automatic transmission, it's from the Titan! Hammer away folks! And the 6 speed, you probably guessed it, a version of the one from the Z car, but with bigger bearings in it (no whining from the trans).