I don't mean to be argumentative, but if I had a dollar for every "post somewhere" claiming things like this, well, I'd be driving a new SL63. I can't tell you how many people stick oily K&N filters on their cars and claim improvements based on "butt dyno" tests. The same goes with chips, Vornados, electric superchargers, fuel line magnets, etc. Maybe there is something special in SeaFoam, but if it really was that great, better than the brand-name gasoline additives, then you'd think MBZ would be telling us to use it. After all, the marque is not shy about having us spend top dollar on high-end chemicals like $7/qt oil and $12/qt transmission fluids.There was a post somewhere, a M271 powered C Class, with carbon buildup
causing poor compression due to the valves not sealing.
They used Seafoam and ran the compression test again, and it solved the problem
A friend of mine ran into issues with her 2003 C230 and I gave her the same advise, and it's been working for her. Same thing, she had compression checked before and after, and Seafoam removed the carbon preventing proper compression due to build up on the valves or seats.
I've never tried it on my car.