Searched & searched and haven't really found a definative answer to my specific issue so, here goes...

My '94 E320 Cabriolet has an idle surging problem; not a huge surge but enough to be obnoxious. When the car is in gear at an idle, the RPM will jump from 550 to about 750 for a moment or two. This also seems to happen in reverse. Can't say for sure that anything else is wrong but I think my shifting might be a tad rougher than it had been.

Have seen a lot of references to vacuumn leaks, to Idle Control Valves, to MAFs, etc. etc. in the persuit of fixing a rough idle. How do I narrow down the hunt?

BTW, new motor mounts about 3k ago