My E31 head (suppossedly) had extensive work done to it. 1mm larger then 280 valves, new cam, ported etc. It's got a very large cam. I can get the lift/duration if your interested. It is quick.
The car came w/ OER 45mm and I didn't feel like trying to find parts for the rebuild. So I bolted on the SU's w/ the N36 manifold. Supposedly my motor was dynoed at 200 crank HP w/ just SU's. I'd guess anywhere from 20-40 HP increase if I kept w/ the 45mm. I think the heavy cam could have really benifitted.
I say suppossedly because the information I got was from the person who built the car, not the guy I got it from.
My car is pretty quick, but no where near turbo fast.
I run the E12-80 Zx dist which triggers the MSD 6AL.