remembering back on all the stuff I tried I think it's fuel but will wire the choke open just in case. I bought the heads years ago and forget all the specifics. it has ferra valves,bronze guides,titanium retainers and hemi race springs what ever that means. they are single with dampners.
anywho,when changing jets I could move the falloff point a few rpm's up or down with a performer intake. swaped in an rpm intake and the fall off occoured closer to 4500 rpm so I rejetted and got it back up to about 5200.

I have a question about the fuel pump rod??? when I changed pumps I measured the rod and it's not quite up to 3 1/4",measured with a caliper. the rod is in good shape but came from 440 source. thinking it could be the rod. are these rods exactly 3 1/4"?

I had a 340 with crane cam close to this one with stock valvetrain and a six pack and that thing would spin up to 7 grand. but remembering I did have rhoads lifters in it.