I have just installed a pair of HB’s in a strat type guitar, when I touch the strings there is a loud grounding hum which becomes a squeal with the volume going up. Things I have noticed is when the front pickup is on there is a slight click if I tap the back pickup with a screwdriver and the reverse when I switch to the rear pickup. The hum is very minor if I only touch the metal jack plate. If I touch the bridge it is the same as the strings but if I touch the bridge and jack plate it drops down markedly. Any suggestions as the where I start looking.