2000 V70 SE, NA, 255K miles

Have consulted with a couple of local Indy shop experts who work on Volvos for a living.
The car still has intermittent misfires in #3 cylinder, which the codes confirm.

Shops’ compression and leakdown checks are good; all five cylinders show 160+ psi.

Have swapped around plugs and coils several times to confirm all are good. Had a fuel injection system service performed. Cleared the codes. Runs like a top until... cylinder #3 misfires and CEL lights up again. So far the shops are stumped about the intermittent nature of this issue.

Last night the car ran fine when parked. It sat outside during a rainy damp night and when started this morning, very rough running and CEL lights again.

Today I reverted to old school trouble shooting myself, pulling off coils with engine idling and listening for the arcing spark in each plug well. #3 had no spark at first, until I removed and replugged the #3 coil connector several times. Finally, the arc and spark returned to #3. Engine smoothed out and after driving a while the CEL went off.

I’m thinking that the four-prong coil connector is the culprit; or a second possibility is one or more of the thin wires leading into the coil connector are internally broken or frayed.

I’ll start with the connector: Is there a way to tighten up and/or keep dry the plug connection into the coil? Cable ties cinched down in some way? Cleaning and dielectric grease on the contacts?

I think I’ve narrowed this down. Now to achieve continuity to #3 coil without internittent misfires.