The shafts look identical, with the shallow recesses in the shafts on either side. If by 'ribbons' you mean the thin teflon strips that serve as bushings on either side of the shafts, that is the part. Hopefully that will tighten things up, controlling any air leaks has a big effect on being able to make effective adjustments to the off-idle settings.
Glad to hear things are progresssing... keep at it!