[belundy]

I can't think of how you easily treat this from a maintenance routine. The deposits come from exhaust gases. Any B12 you put into the fuel system or intake would be combusted on the exhaust side.

You'd have to install a heat resistant "port" on the manifold side of the EGR valve, where you'd inject B12. Let the engine suck on that for a few minutes, then shut it off overnight for the fluid/vapors to do their thing.