youtube how to use seafoam. if you put your vac line right in the seafoam can you may draw too much. when I use it I very slowly pour the seafoam out of the bottle and have the vacuum line from the brake booster suck it up out of mid-air more-or-less. 151k isn't that high mileage for a 2.3. I would change the wires and plugs, seafoam it and see where your at then.
oh, and don't let your friend help you with it, I don't trust him, lol