So Im trying to do a favor for my friend who is clueless with cars. He has a Forester and wants to sell it but it has a misfire in cylinders 3 and 4. I can't seem to figure out what is causing it, we replaced the coil, and spark plugs. He has even taken it to a few shops and they can't figure it out. Has anyone experienced this before, I am hoping maybe this is a common issue with these cars.