I do not agree with the comparison of the 3.2 vs the 3.3t engines.
OBVIOUSLY if you want 500+hp using a 3.3t you must ditch the CIS. You can purchase modified fresh 930 engines for around $10K and have a very good platform to hit 600hp with.
Use the 3.2 FI that you have and sell the rest for a few thousand dollars to use for further upgrades.
The 3.3L gives you a lot for free - low compression and a turbo oiling system, to name a couple. Modified versions will come with the obligatory $2500 exhaust, big turbo, and big intercooler.
Bottom line is you would have an engine that was made to be turbocharged for less total monitary outlay than doing the same mods to a 3.2 Carrera engine.
Just throwing ideas out, it certainly doesn't matter to me how anyone goes about extracting more power - that IS the goal after all.