#1
Ok so I finally picked up the BQS 3 band EQ for my 5 string bass that already has EMG P/J pickups in it. After finally getting everything to fit in the cavity I know have a buzzing noise whenever I touch the pickup housing. It's dead quiet otherwise and I never had this issue with the pickups with just tone/vol pots.
#2
Sounds like a grounding issue to me... check your soldering joints on all ground wires including your imput jack.
Id say worst case scenario, get a cheap voltage meter and check all conections with that and make sure you didn't cross any wires or soldering joints anywhere. Its a good idea to put shielding and shrink wrapping on all wires.

hope this helps bro...
#3
Well there are no grounds or solder joints, its all EMG solderless connections and actives don't ground to the guitar.