I would also ask that you fill in your profile with your location and car and I hope you're in NESIC (my region) because you've provided the most intelligent approach to your car that I've ever seen in a n00b. I'd like to say that I'm doing exactly the same thing as you to a car I've recently bought but I don't have a lightweight flywheel and I went directly to wastegate pressure from stage 2.
For exhaust, people on nasioc seem to swap them like they're motor oil. You can find what you want at a good price local to you (unless you're in north dakota or something) without a huge wait. You can also offload stuff like the mbc and bov because there are people who really, really want to hear the pssssssh.
The car I'm working on has a nice advantage.....STi 6 speed in a WRX. What a shame that I've brought it back to stock power, huh?