I Seafoamed my YJ this weekend. I sucked half a can through a vacuum line, and I divided the other half can between the four cylinders. I pulled the plugs and poured it in the spark plug holes. I let it sit in there for 24 hours, while turning the crank over by hand occassionally. I cranked the Seafoam out the cylinders, replaced the plugs and fired it up. It idles smoother, and the suprising thing is that I have more engine vacuum at idle. My Boost gauge used to read -.5 bar at idle, now it reads -.8. I don't know exactly how that translates into inches of vacuum though. Either way, it is pulling more vacuum at idle. I'll take it for a ride when I have time (work sucks sometimes) and see if I can notice a difference.