[Rick Parker]

From my experience of Weber carb tuning (Small block) if the engine accelerates well, idles well, but has an intermitant "Skip" (for lack of a better word) while at cruise it is related to the emulsion tubes and the cruise A/F mix. With foot to the floor and low vacuum, the E tubes have little to do. While at varying degrees of part throttle and higher manifold vacuum the fuel is being emulsified at varying rates within in the main well.
Is this constant when a certain RPM and light throttle is reached??? Is it heard in the pipes, more than felt? If so, bring it to that RPM in 4th gear, for instance 2500-2800 RPM; then apply VERY VERY light throttle while attempting to accelerate slightly. If the symptom stops, (listen to the pipes) it can be remidied by a slightly different E tube. (Eliminating some of the small lower holes). In my case going from F7 to F16 solved this symptom without any resulting jet changes.

Eljaro you have admitedly done an unusual amount of experimentation with E Tube modifications, perhaps you are overworking one system in lieu of another???

I don't think the fuel level change is causing your concern. If so, it would be apparent throughout the entire RPM range, with more dramatic symtoms.
You might also check the distributor cap for ionization or carbon tracking.