I wouldn't recomend an E-31 for a turbo motor is what I probably should have said

Now for my NA 240Z, well I've been looking for an edge.....

If you were planning on pulling the Turbo and replacing the dished pistons with flat tops, the E-31 would be the better way to go. The P-90 has larger valves, and better to flow than the E-31 so you're probably better off to do some other upgrades and leave the head you have on there as is.

Bigger turbo and/or an intercooler would do more than good than anything.