[MetalMan]

The middle screw on the diff is how you control how tight the diff will be - and by tight, I am referring to how much slip it will have (the tighter the diff, the less slip).

If you tightened up the diff (through the screw) and it didn't help, it probably needs to be rebuilt. I'm sure you can buy a rebuild kit somewhere, which should include two steel donut-shaped rings, two small rings, and a bunch of steel diff balls.

As for the bushings, I am of no help there - never owned a Losi.