All the additives can do is bind the extra water (which the alcohol sucks in from the air) into a finer suspension so it gets burned instead of sitting in your tank. There's no magic that gets rid of the alcohol or the water.
SeaFoam is funny stuff, if you read their MSDS. It consists of naphtha (the base stock in gasoline) plus isopropyl alcohol (the cleaning agent) plus light oil (to compensate for the scouring in the cylinders from all that alcohol).
If you're planning to "blow out the carbon" you can just pour in some old rubbing alcohol and get about the same effect. Or yesterday's coffee, as many fine mechanics swear by. Same effect, the water becomes steam, cleans out deposits. Add in some used motor oil if you want that extra lube.
There's a reason some stuff doesn't have a big ingredients label on it. :-)