To Shim or not to Shim

[Slydynbye]

As far as I know I can get better midrange response by adding shims to the Carb diaphragm needles. Has anyone done this?
Can you share your results or regrets? Butt Dyno results? Gas mileage effects?

 

[bdalameda]

This will definitely affect you fuel economy negatively as the Jet needles really change midrange right where you cruise at on the highway.