I was discussing Seafoam with a local parts counter guy, he seemed like one of them that actually worked on cars and knew what he was talking about. I mentioned the Berrymans, he said he liked it, but not recommended for diesels. He tried to sell me a can of Seafoam on sale for $7.99, told him I get it regular price at Menards hardware for $6.49
I'm not sure the STP is exactly the same, I'll keep using seafoam as long as I can get it fairly cheap.
On a sidenote, people think it is cleaning due to the smoke it puts out...that's the oil it's suspended in burning off.