CRAP! I'm smoking!

Look closely at the plugs; if a dull, carbony black, that points to a slightly rich tuning issue or too cold a plug, not oil. Oil will be a shiny black and will not smell like gas. I am with RRR and others: don't get to caught up in the plugs being different colors on opposite sides; not unusual. The symptoms point to an intake, stem seal issue so focus on that. BTW, I ran Total Seal gapless rings in racing years ago and they sealed up fine with my normal break in process. (Did not experience any special benefit from them so went back to normal ones.)

I WOULD suggest you look at the plug reach while going through all of this; the black is much further up the plug threads than I would ever expect to be normal, and it looks to me like the reach is to too long.