N/A tuning is more about how all the bits work together and finding bits that work well together, rather than expecting big gains from replacing just one thing. My old EP3 Type R was quite tuned up and ran good power of ~248bhp up from the standard ~197bhp mark.
That had a full manifold back system with de-cat, different intake manifold from a 2.2 accord I think it was, an ITG enclosed intake and something called a KPRO ECU which was then remapped to suite. I did all the mods over a course of two years and every one added something. It wasn't until I got the ECU and had it all mapped properly that it all came together. That in itself gave a lift of about 5-10bhp across the rev range and 15bhp at peak and also massively improved the torque curve. Don't underestimate the power of a remap when N/A tuning, it really does make all the difference. Just do it LAST once you're where you want to be, otherwise you'll have to have it done again every time you add something.