my experience with those carbs is that they are jetted way too rich out of the box and i down size the squirter. an over rich condition can feel like a lean condition at times. they have .110 needle and seats with the small afb float. i don't think that float controls the fuel very well with the large needle and seat and that causes the pressure problem. the afb .101 needle seat will flow enough fuel, if you can find them. i think the larger brass float like what the 440 avs's had will help flow control. they're a different animal to tune vs a holley, but i do believe they are more reliable. i had to "go to school" on these carbs when tuning a ch28 and trying to make a smog avs run and drive smooth. basically i like them but to tune them one needs to get their head out of the holley box.