The high comp is a bit mysterious, but if missing long enough the bore/piston tends to let oil past the rings into the bore, with there being little/no pressure of blowby past the rings that occurs normally, this would form a fantastic seal, but I'd still be amazed at that high.
You could well be right about the coilpack, as these do often go, and can affect one side(plug) only.
If all the bits look ok, I would just bung back together, one of the major problems on the older variants were the rocker shafts snapping, but should be sorted by KA time.
tabetha