Are you referring to something specific to the B&M? If not, then this topic was put to death years ago! Dozens and dozens of people leave it out and dozens have left it in. I tried it both ways and I left it out, but then I don't have a B&M, I have a steeda.
The shift tower itself is spring loaded and this will center it to some degree unless the shifter is full of slop from worn parts anyway. At least on 98+ transmissions.
Former owner of '99 CSVT - Silver #222/2760
356/334 wHP/TQ at 10psi on pump gas!
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'05 Volvo S40 Turbo 5 AWD with 6spd, Passion Red
'06 Mazda5 Touring, 5spd,MTX, Black