HHmm interesting. I have the same sort of problem with my 250. HEI, 'New' carb..Still has a stumble and fart about 1800 rpm when I put my foot into it and the auto box is in third. (no kickdown cable) Sometimes it happens when cold in the other gears. It was stumbling and fart real bad, but that was a cracked rubber vacuum plug. Fixing that helped alot, but there still is the intermittent stumble.
