Very Slight increase in idle!?!

[BenzOnline]

Recently on my 126 the idle has increased by maybe 50-100 rpm (bareley noiticable on the tach) but enough to make the gears jump harder while changing from R to D etc. Sometimes when I have AC running then shut it off the idle is not the same but gets back to normal quickly but now its been 2 days. It happened pretty much overnight cause in the morning it was like that and still is now.

It is not the idle modulator (black box) cause when I had that go last yr it was all the way up to 1800 rpm.

Where should I look? Again its a slight increase but not too noticeable on the tach....though its noticeable while at standstill in D at a light.

thanks