My 421 0 1/2 pump with 33 nozzles I had to run a 130 pill to get rid of the miss. 31/98 pill worked ok but I changed pump to an 0 pump and the car is way more consistent running 33/94 pill then it was with the 0 1/2 pump. Everyone says the pump it to small and maybe it is. Only 45psi but it runs the most consistent with the lower psi

I have ran over 150 PSI and I have ran 40 PSI all works the same when tune up is right.

What is important is getting the right amount of pounds of fuel per horsepower and it does not know or care what the fuel pressure is with in reason.

^^^^^^ This

What kind of A/F ratio's are you guys with o2's seeing?

Two cents to think about:

First unless you have a stout SBC the 0 pump is likely the one you should use. The larger pumps don't fit the fuel curve those motors need so the only fix is lean out(s)! because you can't get enough fuel down low without getting too much up top or just the opposite. Pressure is a function of supply vs restriction but a high pressure tune works better once you start making more than 1.8 - 1.9 HP/CID. Before James Monroe got involved with these systems I saw many struggle to get them to run correctly because these systems were too big. The easiest way to tune a system that needs a hi speed bypass is with a data logger with O2 and fuel pressure vs rpm. O2 on a gas scale about 11.8 but it could vary depending on the sensors and the motor. Without this info, good luck! Lot's of trial and error.

I’m running mine at 4.8-4.9 and it’s the most consistent there. I don’t see how anyone could run the 0 1/2 with a small block unless it’s healthy. With the 0 pump I’m running a high speed leanout to get the fuel curve close. Like top said the car will leave fat. Lean out in the middle then go fat, 02 and fuel psi is the only way to get it right. I’m building a 447 and hoping to be a touch over 800hp and I’m not planing on changing pumps