Who is this camaro guy? Do you know anything about cars or are you on here to try and sabotage as many mustangs as you can with your crappy tech advice?? What the hell are 50cc injectors?? Sure you dont mean 50cc accelerator pumps. And pump size is only to cure the lean condition created by a slow reacting fuel system in the carb as you quickly pump the gas. It has really nothing to do with the overall rich or lean condition in an engine. And a fuel pressure regulator will never lean out your carb. All it will do is stop gas from filling up the bowls correctly, and then you run out of gas when you floor it.
As for your carb its too large. Use a 600-650 carb. I'm pushing 625 horses at the flywheel and I'm only using a 700. A 750 has larger venturis which means your engine needs to try harder to suck enough air past the boosters to get fuel to be sucked out of the bowls, through the carb, and into the engine. This is the reason a larger carb runs great at higher rpms, but runs like crap at lower rpms. Will it run? Yes, but the streetablility wont be great, and unless your a really good tuner, you will have off idle stumble, and bad gas mileage. Being a DP makes things worse because its going to pump gas in your engine whether it wants it or not. \ /
/ \ That is what the carb venturis are shaped like. Its this shape that creates a vacumm as your engine draws air through the carb. Its this vacuum that makes fuel move through the carb. Its like sucking through a straw, I'm sure you can move a lot of soda through one straw, but try sucking soda through a hose or pipe. Harder isnt it? If your engine cant move enough air through the carb to extract gas then it wont run correctly in the low rpms and you may backfire through the carb or hesitate due to running lean. The good news is you are in better shape because you have a manual, but this only helps in drag racing because you can sit there revving it before dumping the clutch, but low idle cruising will create a problem. Go to a smaller carb. Hope this helps.
