Thanks for the tip Boris! One of the rare seafoam stories that actually has a positive conclusion - for a change. Any effort to clean the injectors (on the bench, or additives) can help restore a clean spray pattern and this can add on an MPG or so. But you can do this with any cleaner product, even straight kerosene, which is the main ingredient in most of these 'products'.
Here is one comparison showing what chemical cocktails are in these 'snake oils'.
Comparision of some injector cleaner ingredients | Fuels and Fuel Additives: Gasoline and Diesel | Bob Is The Oil Guy
and the main ingredient in seafoam?? Naphtha - good ol lighter fluid! I would guess the additive packages in most pump gasoline (at least here in CA) contain many of the same ingredients.