Remap is the best $400 I ever spent. Was done on a dyno.
With the standard ECU as soon as you add a big exhaust and up the boost they run ridiculously rich ~10:1 afr. With the remap I had it leaned out to 12:1 throughout the rev range/load points. In turn I get MUCH better economy, power is up from 127 to 151rwkw. More top end, smoother idle. Its just so much better. Had the speed limit removed as well.
Highly recommended, just as good as a stand alone ECU as they can do timing and fuel. You still retain your standard knock features, excess air flow cut (if say your waste gate hose splits).
I got mine done via the speed lab, he should be here on these forums do a search. R33 computers are very hard to remap so not many people do them, if any at all.