The results:
Since the installation I've participated in three autocross events. Shifter movement is noticeably reduced, and (this is a seat of the pants gut feeling) it seems that the shifts are slightly quicker and more accurate.
In daily driving I have not noticed any increase in vibration. And the shifter movement from gas on/gas off has been greatly reduced. Everything just feels a bit tighter all around.
Overall I'm very happy with this (albeit minor) upgrade and the improvements that have come from it. So if you are are looking to tighten things up in this manner, I have no problem recommending these bushings to you.
And I'd like to thank Ryan for putting up with all of my stupid questions along the way. Despite all of my attempts to make this more difficult than it turned out to be, he was very patient with me and was of great assistance.
