Unwanted buzzing could be a few different things.
1. You could have a bad ground.
2. You could have it wired wrong. (Very easy to do)

You see, basically in order to get the noise out of the pickups, they sould be wired out of phase with each other. That meaning one should basically be north, and the other south.
If you did this, check your grounds EVERYWHERE... One ground wire off will give you noise from hell...

Shoot the pot with tuner cleaner. The pot could be brand new, just sitting around collecting dust. Dust makes it scratchy...