I think I've got the same problem. I took out #1 injector only to look at (not wet/leaking) but I replaced the small rubber seal with a new one. The insulators are plastic. No need to replace but note the orientation of them (there's a hole through the middle). I've got the stumble at restart too. My idle is also not smooth so I'm thinking a bad spray pattern. I've been reluctant to replace them because of less than 50k miles and with other CIS-E cars never needed to, even after 100k+ miles. Oh well. Maybe I'm lean at idle but without an exhaust gas analyzer I've no way to know. Runs great otherwise so I've 'lived with it.'