Clean your IAC 1st, you should see an improvement.
After your engine warms up try (while driving and the hi idle is occurring):1. push in the clutch 
2. turn off the engine 
3. turn key back on position 
4. let out clutch.
If the high idle disappears you have the same issue as me... I have given my subaru mechanic carte blanche to fix this but its gonna be 2 weeks before he has an opening. Someone on the Samba lists reported that flashing the code on the ECU fixed his similar issue.
 Sean G

      From: Vincent Dow <ianvincentdow@GMAIL.COM>
 To: vanagon@GERRY.VANAGON.COM 
 Sent: Thursday, November 10, 2016 7:39 AM
 Subject: Racing idle in the cold (1995 2.2)
   
Hiya subaru-vanagon heads,

I'm driving *Modesto* around Montreal these days, and the temperatures are
getting lower and lower.

In past cold weather, I've had this recurring problem of the idle sticking
at 2000 rpm.

Again, *Modesto* is a 1982 Westy (air-cooled) converted to 1995 EJ22.
Kennedy conversion.
Hard worker and incredibly reliable.

The cold weather really bums him out. This idle racing is incredibly
annoying tho. Difficult and perilous to change gears (esp. reverse at that
high idle)

And I get a pretty regular check engine light in this circumstance, at
which time the idle DROPS almost to a stall, and sounds CHOPPY. Loss of
power. Then that light will go out, and power returns, but the idle stays
high.

I have tried to pull a code by grounding the green test lead off the ECU
(and we did get it to start slowly flashing) but it never communicated a
code that we could interpret.

I am thinking IACV... maybe some gack built up in it.
The Check Engine Light/low choppy idle phase is reminiscent of an open
vacuum line - the way that sounds and feels. But it's intermittent. Would a
stuck IACV eventually cause such lean running that the ECU tries to
compensate..?

Any input or experience seriously appreciated.

Modesto is going in to our favorite shop this Fall, to have spare tire tray
restored, and some other stuff like a leaking heater hose at the front core
when climbing serious mountains. I'd love to figure out this cold running
difficulty.
best
vinnie