Yes.

I recently found a vacuum leak using propane. Was pointing a hose from a propane cylinder a every joint and rubber elbow I could find. On the flame trap housing (which has two hoses attached) found I could modulate the idle when pointing the propane at the end of the smaler of the two flame trap hoses. Took a plastic tie-wrap and cinched the hose tight. Was no longer able to modulate the idle with the propane.

I am watching this thread very carefully because I also have a rich idle on my '96 855. The propane cured that minor vacuum leak, but that was not the cause of the rough idle.