My 190E is running rough, seems to misfire on 2 cylinders. What to look at?

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Hello. I've purchased a '93 190E in great condition with the exception that it is running rough and seems to misfire on 2 cylinders. Once it's up to speed it seems fine, but not at idle. Could this be timing, some sort of sensor, valve or ??? Any thoughts as what I should look at? Thanks for any help. Geof