I did a SeaFoam treatment on the MKT this afternoon and there was definitely more carbon in there than I realized. Afterwards I scoped a few intake valves and the piston top again and there's a noticeable improvement. While some carbon still shows up in the intake manifold it's so soft that a good drive will likely burn it out. The carbon goo was coating the borescope camera after scoping the intake.
Here's how the exhaust filled my garage after the SeaFoam application:
And here's one of the intake valves, shiny clean:
Now the top of piston #6, notice the carbon build up around the edge is gone today:
And finally a close up of the center top of the piston. The machining marks are even visible:
-Rod