The reason a lot of you are having bad changes is because you followed the instructions that came with the B+M.
Try assembling it on kitchen floor(including the long rod),then offer up the clamp (don't tighten yet)
to shifter shaft THEN bolt unit to the floor of vehicle. Then and only then
tighten clamp on shifter shaft/this ensures that it all bolts up nice and 'square' and each shift should be as smooth as me!
Good luck.

P.S.
If your box is a little 'doughtful' a little 'slick 50' also works wonders.