Could excessive vibration and a different sounding exhaust be the result of an electrical problem or would one lean more toward motor mounts? I have replaced the plugs.This vibration even radiates into my hips and lower back. Thanks

 

Vibrations are normally caused by moving parts. An electrical problem that effects the engine could cause a problem but you would notice the engine sound quickly. The first place I would check isthe primary chain for correct adjustment. A loose primary will cause vibration. If you have added a Backrest especially a tall one, this could contribute to a vibration at a certain engine speed. "A" models have rubber mounts and "B" models have a internal balancer. I have seen one Night train that was heavily modified for street drags that caused the internal balancer toslip on the shaft. This caused such a vibration that it caused the frame to crack. Harley warrenteed this although the bike was a 124 cu in fire breathing maniac.
If you can't locate the problemlet the shop take a look, They should know just where to look.