92 Skylark Quad 4 Sparking From Crank Pulley to Timing Cover Bolt???

Ok this is a new one to me. I work for a used car lot and am pretty used to the GM turn signal switches and ignition switches by now. But this car has my perplexed. It started with a a slight miss. Pulled the cover and put in new plugs and made sure all the extensions were seated right on the plugs. Then two days later it is back with a nasty little spark that jumps from one of the timing cover bolts to the crank pulley itself? I have never seen anything like it. I figured it must be a bad ground so pulled all the ground straps and cleaned everything up on both ends and the bolts and some of the paint on the body grounds. Still there. And we noticed that it gets worse at higher RPMs. So I replaced the crank sensor and it stopped for about a week, but has no started up again. Tried another crank sensor and same thing. Any suggestions?

my car does it too but it runs fine

I would add a groundstrap or two from the engine to the body.