I'm not at all sure I buy that; have you ever seen any scientifically derived proof of the efficacy of Seafoam on an engine with heavy deposits?

 

Your skepticism may be well placed.
I used "Seafoam" in 3 cars and I had better throttle response as a result of that. But that does not say that deposits have been removed.
After poking around with Google I found that "Seafoam" is the solvent Naphtha + oil. I also found that Chevron found a chemical called Polyether Amine (PEA). And that stuff is said to actually remove deposits in the combustion chamber. It is the active ingredient in Techron.

I copied this from another board:
"PEA is used in varying amounts in almost every quality gasoline made. The problem is unless you use one from the day an engine is new or rebuilt it takes time to clean things up. That and the amount varies from one fuel brand to another. The way to overcome this is to use a PEA based cleaner a few times a year or with every oil change and a good quality fuel (www.toptiergas.com) in between.

Typical fuel cleaners are solvent based and therefore cheap. They don't do much other than make your idle nice and that isn't from any cleaning action. PEA cleaners cost more because PEA is expensive to produce compared to solvents but also far more effective. The leading PEA based cleaners are GumOut Regane (yellow stuff in clear bottle), Redline SI-1, and Techron Concentrate. Each of these products has any where from appx 30-50% PEA with RedLine SI-1 having a slight edge. The cheaper Techron ProGuard also contains PEA but at a lower concentration. Not a good value.

Gumout Large Vehicle System Cleaner in the gold bottle is also PEA based. It contains the same percentage of PEA as does Regane but in a different carrier. It's 20 oz size makes for a better value if you can find it. Be sure it says "fuel system cleaner" and not "fuel injector cleaner". The bottles look nearly identical but the fuel injector cleaner contains no PEA."

I will try it.