No point really in switching heads. The ITR head is essentially a B16A head with a minor port/polish job done to it and of course the assorted valvetrain upgrades.

The hottest cams I've sen are the JUN III, or copies thereof (for example skunk2 Stage 2). I'd go with those cams, but you'll need stiffer valvesprings than plain ITR ones. You can use ITR inner springs with Portflow outer springs and that will be sufficient. You also want adjustable cam gears to tune the cam timing.

From there, you definitely want to make sure the exhaust is nice and uncorked. At the minimum for this kind of setup you want a header with a 2.5" collector, a 2.5" high flow cat, and a custom exhaust made with 2.5" pipes going back to a muffler with a 2.5" inlet. The key here if you didn't notice, is 2.5".

As far as what header to go with, they run the entire gamut of price and performance. At the low end of things you can go with a 98-up JDM ITR header or a DC Sports 4-1 header designed to bolt onto a '98-up JDM ITR. These both run under $500. From there, you can go for any number of exotic headers which sell for $800 on up and will gain you another 6 to 10 hp at the wheels on a highly built motor compared to the JDM ITR or DC header.