...is I own 4 older MBs (LOL)!

I'm having an erratic and somewhat higher than normal idle problem - usually 950 - 1050 rpm, sometimes normal around 650- 700. It also fluctuates while sitting just enough to hear the RPMs changing without registering on the tach (above numbers are while idling in Park).

ICV seems to be functioning so I thought a quick swap with a known good ICU would either identify or eliminate a possible cause.

You say "behind the kick panel" - do you mean passenger side footwell wall?

Regards,
Kevin

__________________
"Dangerous with a wrench...and not smart enough to know it"

Stable (in order of acqusition):
'84 500SL, 280SEL (Euros)
'77 280SE. '90 560SEL
'79 450SEL 6.9,
'95 C280 (totalled by daughter 8/07)
'81 280SL (rescued) '88 300CE
'86 560SEC '95 C36
'01 CL55

DD's: '04 S500 4Matic (SWMBO)
'04 F150 Crew