Vacuum Question
Changing the position on the accelerator pump arm usually is something that's done to an older carburetor to get it to function better. I had several stumbles and things due to the wrong size Jets and definitely due to not having strong enough Springs in the metering rods. The right weight spring and metering Rod helps a lot especially if they're is a performance cam or something in it.
You could have had a blocked passage or bad gas or something? But the accelerator pump is basically just for tip in. Not at the 1500- 2200 RPM Mark where you're talkin. Possibly in lieu of needing a bigger jet or smaller metering rod you're over use of the accelerator pump maybe a making up the difference?
