If you're tracking the car I'd be looking at where you might need to change gears with the different diffs on each circuit and go for the best compromise.
Remember that with the blower you won't want to rev it as hard to keep stresses down..and I don't think the std FI Dynotronics tune gives a rev limit increase
For road the 3.7 will be perfect with the extra grunt available.
BTW there will be, very soon, a facility in NSW doing the Dynotronics tunes,according to rumours, you might be able to negotiate having the tune done there rather than the extended process of sending yours over to the US. It'll also allow you to get the usual (in the US) free tweaks after logging or a dyno session to get the tune perfect for your car.
Oh and if you're selling that diff...let me know!
05 NCLE, Cosworth SC,PF01,Ohlins,Selby,GWR exh,TDR tune
"We're only given a tiny spark of madness.We mustn't lose it"(Robin Williams)