to carb or not to carb?

[mister.freeze]

OK, I've had Holley's ProJection 2d TBI for the better part of 10 years on the Fox's 383 stroker. I've run it in both big an small block mode, with and without the closed-loop O2 sensor. I just feel that I've never gotten the best out of the stroker. The mpg has settled in at about 9.16, with or without tail/headwind, up/downhill, trailer or not, top on/off. ANYBODY have an idea what cfm a motor like that needs? The ProJection is rated at 650. It's been VERY reliable and works well, but I know there's more to be had out of my motor, especially in the mpg department. Should I carb? Go propane? Leave it alone? I'd LOVE to go diesel...