Ah, yes, the dreaded seepage of oil just behind the evil cover on the passenger side. Kinda runs down toward the chain adjuster plug - and if it gets bad enough, it runs all the way along the underside of the head and down the right rear of the engine.
It sure looked like a head gasket to me, but it was indeed the cover seal.
Seems to last about 5 years, and starts seeping again.
actually, mine is seeping a bit right now, so here we go again (4th time).
- Sounds like you cleaned everything really well - I use a sharp pick to get every little spec out of the groove where the seal butts up to the head.
- There is one bolt, lower driver side, that screws into a threaded hole that is open to the oil passage. This bolt should have a dab of sealer on the threads.
- I found the best lubricant for the seal to slide the cover over is "spit".
just spit on it, slide the cover on; the saliva then dries quickly and the rubber sticks well to the metal cover. As directed in the manual, I only use sealant on the ends of the seal (and of course on the metal mating surfaces of the cover and head.
- if the radial seal is leaking, you should be able to see traces of oil under the rotor cap, so that should be easy to rule out.

Good luck,
DG