Do you think that a treatment with Seafoam once in a while would keep the valves clean? I've never used it.
Ford sells a special intake valve cleaner just for this purpose. Can't say if it's any better than seafoam. I seafoam (through the intake) every year or two on my duratec and when I had the intake off the valves were spotless. Did it do anything? I dunno but the valves are clean, they could have been clean with or without it though.
Would it be better for the ecoboost? Again I dunno, but since Ford is selling a product for it I would think so. When my mom's edge is due (2.0 ecoboost) I'm just gonna let the dealer do the decarbonizing themselves, that way if they hydrolock the engine they can pay for it. Not worth me dumping chemicals down the intake on a brand new $40,000 car. A 12 year old ranger I got no problem doing it.
But again, you are putting liquid in the intake, a little too much and the engine will hydrolock and become a boat anchor. Never seen it happen but it is theoretically possible. Risk vs reward...