Seems you are dumping solid liquid balls of gas down your carb. My 350 chevy 4 bolt main with a 750 double pumper did the same thing. It was adjusted fine and everything. Turned out to be the grommet seals sold to me by the braided line I bought. The seals were not gas proof and desintigrated. The grommet material got into the jets and just dumped gas instead of atomizing it.

Worked great at idle or 4000 rpms and higher, sputtered and kicked whenever you toutched the gas otherwise. I drove 30 miles in 2nd gear to get to my mechanic's for the fix.