For durability I would put some forgies in there. It really doesn't matter which manufacturer either so don't be conned into putting HKS when JE's are fine. I would also replace the conrod bolts as they are weak and stretch quite easily. Other than that a mild port on the head will also promote better flow. It won't gain you stuff all power as you are limited to what you're factory turbos flow. I say factory turbos as I would presume since you want throttle repsonce they are the best choice.
Without NOS I am making 450hp. My engine is completely standar except a intercooler up grade, pod filters, downpipes, and full exhaust system. I honestly don't see why you would really want to put nos in a car to run autocross on. I have enough trouble keeping the car from losing the ass end around tight corners now. It comes out of the hole like a rocket and once I am above 30kmh or 18mph it is all on in first.
To give you an idea I an accelerate from 0-100kmh or 62mph in 4.2 secs and have run 1.66 60foot times on the drag strip. It is all in the tuning of the ecu.