The carbs need to be reset after installing the Jet Doctors especially on Webers. The whole idle air intake path is changed. I had to reset mine, and had a terrible rich bog from 1500-2500. I put my wideband A/F meter on and found out why. The short velocity stacks were interfering with the idle air BIG time. I installed the original taller velocity stacks and air cleaners and the problem disappeared, back to running flawlessly.
As an aside, the Jet Doctors may be a better idea on Webers than on Dells, but I only have a lot of experience with Webers and their clones. Not much time working on Dells.