Allegedly, the higher flow directly over the jet RICHENS the idle/pickup mixture, rather than the air passing around the circumfernece of the throttle plate. Not entirely convinced.... [&:] My problem is at 1/4 throttle.

The amount of richness required in the mid is in the 1/4 to 1/3 of a turn range (so quite a lot). That is with the low end set at a very best idle. I've got several carbs, so drilling and welching and possible FUBAR are not a problem
Where do I drill???