We don't have bike inspections in Ca, but they may one day and i always keep any mods i do limited to reversible mods. If you are forced to have it tested, all you need is tuneecu and a PC. Change back to stock pipes, load stock tune, go for test, reinstall illegal pipes and tune.
that said, theres a post about a company doing head work and cams to the Tbird that adds something like 30HP. Thats great, but it's a mod i would never do if i lived in a state where they do testing unless the idea of a very big and heavy doorstop is appealing to you. Even here where they don't test i'd be wary of it because if they start testing tomorrow i have a doorstop.