If you kart is real good It's mostly all tires, or move 5lb of weight left to right or vise versa, however in general If it's off going in look to the front to change, If it's off on exit look to the rear to change, If it's off in center is the only time I'll look to wheel spacing's and there MINOR pretty much set them and leave them alone, Remember MOST exit issues are entry related, Also remember cross is a more fine tune adjustment.
Thanks so much for the advice. What wheel spacing is considered optimal?