Carbon build up on throttle butterfly and inside intake manifold and head ports

Just finished doing the valve cover gasket, spark plugs, and a new No.1 ignition coil. A while back I did the coolant pipe repair/change that runs off the thermostat housing.

First of all, I didn't think about it at the time of doing the coolant pipe and putting this all together, so please don't hate on me. My 06' 2.7 Tacoma has 195,000+ miles on it and is all original for the most part so I thought being older and is left idling quite a bit that it wasn't anything to worry about, and since it was running just fine "if it isn't broken don't fix it". But after doing the valve cover gasket it occurred to me that a possible reason for the carbon build up was a bad PCV valve or if I have some other source of excessive "crankcase/top end ventilation". I tried to find a PCV valve locally, but seriously no parts store had one and the dealer said we'd have to order it. So, while I wait to get my hands on the part I'd like to hear anyone's thoughts on the possible reason for the carbon build up being from a stuck PCV valve that is the original, or if its coming from ventilation in the other vac line that feeds directly to the intake resonator that sits above the valve cover.

I don't have any pics of this since i was in a bit of rush to get these jobs done at the time and didn't a have a camera, but keep in mind that the throttle butterfly is coated with a black dust ring on the outer edges, and the manifold and head ports have what I'll call HEAVY caking of soot that's has a light oil texture. Also, feel free to include possible solutions to cleaning all this without taking it all apart. Like is a good dosing or two of seafoam spray a good start or not?

Thanks in advance for any positive feedback.