Anyone interested in using this or any other fuel additive, here's a real world, empirical test. Pull at least one spark plug and check the color. Then run a full tank treated with Seafoam, recheck color of the same plug. This would probably work best if the plugs are not new but have a few miles on them.
I did this with my 06 Roadstar (notorious for carbon build up and sticky exhaust valves). The plugs were the OE plugs that were in it the day I bought it new. They had about 6-7K miles and were dark brown on the white ceramic electrode insulator and black and sooty around the edge and close to the center electrode. After the tank of Seafoam (At their recommended "Shock Treatment" mixture ratio) the plugs came out looking clean and almost new. I concluded that if the plugs were cleaned, the whole combustion chamber, valves and valve stems, were cleaned as well. No more sticky exhaust valve symptoms either!
Just one mans experience! Some additives ARE Snake oil, I feel I have proven (At least to myself) that Seafoam does what it claims.
Phil