There's a lot of examples of basically the same engine going from Carb to TBI to MPFI to SFI. At each jump the gas mileage improves, the idle quality improves, and the power improves (to a point), and typically the emissions improve. A particularly good example is the GM 60 degree V6. 2.8L Carb was 110hp, TBI was 120hp, MPFI, 130hp. They then switched to an MPFI 3.1L, which was 140hp, and the SFI one was 160hp.
My experience here is that having the manifold be dry flow and having SFI really smoothed the idle and it can idle pretty lean for a highly modified 340. It wouldn't idle worth a crap with the AFR in the 14's with a carb and it easily does it now. Also instantaneous throttle response.
