I just figured that from Craig's post above:
"A local guy had a MOTEC EFI conversion done......with the stock manifold. He was disappointed in the results. 420 RWHP I believe was the max which is right about 500 FWHP. I don't recall the head work/porting etc that was done."
Since I was also a "local guy" to Craig, I thought I'd chime in.
Anyway, if that's what a Motec engine with a 930 manifold can do, I figured the manifold change is worth around 100. But, as I said, that doesn't account for possible variables (including boost--dunno what that 420 hp guy was running for boost...).
This is a project that got out of hand. Bought a 930 on the servicing shop's say so (last time I EVER do that). Crank had been turned twice, pistons installed upside down, rod bearings shot. Had to split the case, and all the rest is basically "while we're in there" stuff. Did try to use a TEC ecu, but never could get idle and cold start right, so went with Motec.
Then I got FM-10s, custom-valved Bilsteins, the right torsion bars, Charley bars, etc.
Runs nicely now, though. Still got some "rawness", but good, solid power. G-50 wakes it right up, as well, and the Wevo short shifter matches up with it nicely. I've never driven one, but I guess it might be similar to a '89 930, although maybe lighter and with more oomph. I've driven a '94 3.6, and that felt much more civilized and heavier.
The money and patience it took to get here, however, qualify me for instant membership in the Idiot Hall of Fame. So I don't talk about the process too much.