Techron for carbon and valve deposits. seafoam in the oil for lifter clickers, fuel for injectors and water in the gas. BG44K for injectors in the fuel, or as an injector flush in a machine.

I use seafoam in boat motors a lot, as their fuel systems tend to gunk up worse with longer fuel sit times and lots of water around.

For real bad carbon deposits, I use water down the carb. The old 6 1/2oz coke bottles were about right. Way back when before steam irons, everybody had a sprinkler cap for a coke bottle to sprinkle stuff when you ironed it. We'd use that, and run the engine at around 2500rpms in N, and sprinkle the water down the carb throat (warmed up engine!!). I bet a spray bottle would work better. This works best with no muffler, NO turbo, and no cat in the way, because chunks will fly. The water steam blasts the carbon deposits off the whole combustion chamber and piston top, and the crap mostly blows out the exhaust. Look at an engine with a blown head gasket and note how shiny clean the combustion chamber is. This will restore lower compression by getting the carbon out of the combustion volume and off the piston crown and out of the quench volume. This latter is most important for killing knock.