Has it always done it (since you bought it)? Does it seem to idle consistantly, but shake the car or is the idle unsteady? If it idles well but shakes, motor mounts are a likely reason. Cleaning injectors is a dicey project. How did he do it? Did he test them on the bench and observe spray patterns? If not, you could still need new injectors. I did a lot of work to mine and when I changed the injectors it made the biggest difference. When it is warming up the fuel enrichment helps with more fuel but at low idle you don't have the extra fuel. You have to ohm the spark plug ends as they go bad. It could be a lot of things. MHO only. Good luck.

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Steve
1985 Mercedes 500SL Euro (Gray market)
1995 BMW 520i Euro (Gray market)
1992 BMW 525it Wagon
1994 Honda Del Sol Si