tom is definitely not your guy for tuning. Randy at FSWerks is easily the best tuner out there for your area of performance goals.
Depending on how much you want to spend, you might be able to get above 170whp (on a dynojet) with Intake, Header, 3" Exhaust, Stage 2 cam, 2.3 Head Swap with Port/Polish, and an intake manifold (Cosworth with modification, Weapon R with modification, or Top Speed Duratec I/M <--best choice)
You could also do a DIY turbo kit like I am. You could put together a non-intercooled 6-8 psi setup for less than $2,000.
Otherwise, FSWerks Stage 1 is the way to go. Check em out at fswerks.com. Give Randy a call and tell him what your goals are and he will hook you up fosho.
The final option, is to go n/a built. 11.6-12.0:1 compression pistons, hard cam, aftermarket I/M, header and 3" exhaust. That will give you right around 200whp.
As for what felix said. You most definitely do not need to swap to a 2.3. I am going to be putting down above 300whp on my stock internals 2.0. The 20 more than gets the job done. You do not need tubular control arms to help put any power down. And the Torsen diff is no longer made so that is out of the question. The stock open diff will be completely fine with your power levels as long as you're not doing a million drags.
If you do decide to keep it N/A, then you will want to have 2 mufflers on your exhaust to help keep quiet with the header. Example, FSWerks Stealth exhaust. But FSWerks will not sell a 3" version of their exhausts, so that will be needed through Trubendz.
If you are going boost, then FSWerks 2.5" Race Exhaust will be perfect.
07 ZX5 - Low and Slow Daily
96 GSX - The Racecar