SeaFoam = best stuff on Earth.
When I had my previous car, I had ordered an SVT upper intake manifold from a salvage yard to replace the incredibly restrictive stocker. Well, the sucker was caked in carbon when I got it. Not even close to half a can of the stuff liquified the carbon and it rinsed right out. Granted, it killed the grass where I did this, it still worked like a charm.
I know plenty of people that run it directly through their engine, either through the fuel system or the vaccuum line, and none have any had any problems with the stuff.
If there was one single product I'd recommend for your engine, it'd be seafoam.