[Dave in MN]

Seeing the oily deposits in the front intake port, I think you may have excessive wear on one or both of the valve guides in this port. If it were mine, I would remove the head, rotate the crankshaft to raise those two intake valves and see if you have excessive lateral movement of the valves in the guides. Grab the top of the valve when in lifted position and try to move them horizontally.
You can check this by taking the valve cover off and looking for the same movement, but it is much more difficult to get to the valve stem to apply pressure.
This condition could also be caused by an intake valve not seating well.
Good Day!