Depends on which part you are talking about.
ignition wise...the 'idle stabilizer' on a 1.9 is a separate unit from the
ecu.
If there is a comparable ignition timing circuit in a 2.1 it would be in the
ecu.

the Idle Control Unit ...the vale and control unit, on the 2.1 ...which have
to do with air control that determines idle speed, and not with ignition
timing control...is a separate unit in the 2.1 system .

one is about idle control via ignition timing tweaking,
one is about air flow control.
different systems that both relate to idle, but are basically unrelated.

----- Original Message -----
From: "Dennis Haynes" <d23haynes57@HOTMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thursday, May 06, 2010 9:03 PM
Subject: Re: Advice on Spare 2.1

> The idle speed controller is not in the ECU on the 2.1. It is a separate
> controller located in front of the passenger side tail light. It can be
> easily integrated into a 1.9 to eliminate that almost useless advance the
> ignition timing before it stalls stabilizer and the auxiliary air
> regulator
> along with those AC and PS idle booster solenoid valves.
>
> Dennis
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> B
> Feddish
> Sent: Thursday, May 06, 2010 7:22 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Advice on Spare 2.1
>
>>> gonna be hard to get an idle stabilizer or ign control unit on a 2.1..
> they're incorporated into the ecu. <<
>
> Ah, you kids and your modern VW's....
>
> ;)
>
> Bryan