ive seen worse pics. as someone else has said- its a pretty dirty engine prior to the PCV change . mine probably has the build up too just not as much yet. i really should get the update

 

You guys should take off an old RX-7 intake sometime. This isn't uncommon. No the type of oil used had nothing to do with this. As far as the fuel not being able to do this due to injector location, that is false. It can. The pulses traveling back and forth in the intake manifold are pretty strong. That's why VDI works. On RX-7's you will even get the back of the throttle plates gummed up. While it's off, clean it and reinstall it.

 

yes, and this is not a rotary specific problem as you should have saw the intake and throttle body of my old Probe GT

its a combo of fuel vapors, oil vapors, exhaust vapors, and the .2% of the dirt in the air that air filters don't filter out (which after 30,000 miles is a large amount... as seen here)