Seafoam is great. I think it works best in the air intake system. Rather than pouring it in a vaccum line (as the link says), pour the seafoam in a cup and pull the PCV valve. With the PCV valve still attached, use the vacuum line to suck all the seafoam into the intake system. It may choke up the engine for a moment but afterward the engine purrs & it cleans the PCV valve.

Have fun