I am woundering if the .020 movement is the culpret. even with new valve seals oil could bypass these. expecially if there is a moderate volume of pressure within the crankcase. I know it is not blowing out the dipstick but if you have a carbon buildup within the intake chamber that tells me oil is getting in that area somehow and the most logical place would be the intake valve/exhaust guides. I mean, how else is any build up of carbon going to get into that intake chamber arround the seat of the valve?
just a thought.