[eschaider]

Low speed engine stumbles (below 2000 rpm) can easily be attributable to camshaft selection, especially if it is one of the cams that provides a 60's style race car idle. Manifold vacuum is typically low with these cams. Additionally cylinder to cylinder charge reversion at idle (which contributes to the race car sounding idle) is quite common.

EFI might mitigate this undesireable behavior to a point, but it will not eliminate it. Sort of reminds me of something I read recently. It said, 'Duct Tape can't fix stupid but it can muffle it'.

To restore good low speed engine manners, you are going to need a camshaft change. The camshaft change will significantly reduce the 60's style race engine rock and roll idle qualities the current cam provides but the bucking and farting in higher gears at lower speeds will go away.