Im a believer in this stuff. I was highly skeptical, but one day it was on sale at the parts counter......buddy told me stories of customers. I bought it, then came home and youtube'd it.
Then I tried it on my 200,000mile 3.8 v6 1987 buick. The entire can of seafoam I let the engine suck up, until It stalled out. I had a hell of a time starting the motor. I ended up pulling the plugs, cleaning them up manually and then it started. Holly Smoke!!!! No pun intended. It honestly ran noticeably smoother after that. The idle was night and day difference. It drove nicer too.
I don't stick anything in the oil though. I don't believe in thinning oil out to clean passages. I use a high detergent oil for that.
The one thing is defiantly change you oil after this and probably your plugs too