I'll get the bad out of the way. The car needs a little work to get back to 100%. Turbo could use a rebuilt. Power wire to the alternator is broken somewhere behind the instrument cluster. Powermaster is starting to whine.
The car has 141k on the clock. Less than 10k on the engine and...
best way would be to put it on a dyno. Boost and timing are going to make a huge difference.
If I were to guess, it would be capable of 500+rwhp comparing it to my numbers and mods.