Yesterday I had my OEM transmission mount bushings replaced with larger and much firmer 320i bushings. I also used UUC's "Enforcer" cups which limit these new bushings even more from compressing and flexing. The stock bushings are very flexible and mushy. You can easily twist and smunch them with your fingers! Not my new ones!
Today I put the new bushings and "Enforcer" cups to the test! Before the change, I definetly felt the transmission move in its mounts way too much. In stock form, if you needed to gear up or down when the transmission happened to be "flexed over" or "twisted" too much, there was a good chance a gear would be missed. Missing an upshift is bad enough but missing a downshift can spread parts and cost thousands to fix, warranty or not!
What I found was a perfect set-up regardless of what I tried to do. Nothing I did made the transmission flex or move (at least not enough where I could tell). There was a sure and confident feeling when shifting during heavy cornering and high RPM. I feel that I now know exactly where the gears are "all the time". That's a nice and reassuring feeling!
Not knowing before the test how much improvement to expect from the new set-up, I was indeed very pleased with what I found. Also, I noticed no additional cabin noise from making this change either. The mod has all positives and no negatives.