I have installed new motor mounts,rear diff. bushing,trans insert and finally shifter bushings. It seemed with each replacement the shifting was better but more cabin noise and vibration each time. I was getting some serious shifter rattle and gear noise so I took out the Revshift insert the other day. I trimmed down the high spots on the top and bottom and stuck it back in there, maybe 3/8" total material trimmed off. I also took maybe an 1/8" of the sides were it touches the OEM rubber. I was basically wanting some height from the insert but not wanting it to be crammed in there. I wanted to give the OEM mount some room to move around under load if needed. So far it seems to be my fix, gears shift smooth and just a hint of gear noise under heavy acceleration. Under normal driving, no gear noise so far. I also was concerned about maybe it slipping out, after several hours of driving it hasn't moved.