Idle sometimes hangs at 2000rpm

[amd is the best]

This is kind of tricky to describe but I'll do my best.  Also, I don't have a log of it taking place yet but I'll work on that asap.

Background:
1991 Audi 200 20v 3B
EFI Express PnP VEMS System
Firmware 1.1.95

I'll be driving at say 3500rpm, push in the clutch/let off the throttle to come to a stop and the car will drop to about 2000 rpm where it sounds almost as if it's hitting a rev limiter.  The "idle" bounces up and down fairly rapidly, fluctuating between ~2000 and 2300.  In VemsTune I see the IAC on/off indicator flashing back and forth with the bounce of the "idle."  Does anyone have any idea what's happening?  I've tried looking through all of the idle settings and can't quite seem to figure this issue out.  To get it to stop, I just bog the engine down to where a normal idle is and it stops.

This will even happen sometimes after using the launch control feature.  Bring up the RPM's with launch activated, let off the throttle (no actual launch) and as the rpms come down it'll stop at 2000 and start doing it.  Sometimes even just revving it up it'll do this.

Related or not, I also have the car stall out on my sometimes when letting off the throttle.  It can't quite catch itself and stalls out.  Usually I'm rolling so I can pop start it.

Any info on this would be greatly appreciated!

Thanks,
Nick

[amd is the best]

Here's a quick clip of the issue: http://www.youtube.com/watch?v=Bh3YRxQryWA

Here's a log of the issue: http://www.njsphoto.com/temp/v3.3_n003073-2012.05.12-05.46.41.vemslog

[mattias]

It's overrun fuelcut. You can disable that, but it's not the root of the problem.

You should let the idle air control integral have much more power, +/- 20 isn't going to get you anywhere. Set decrease to 80-100 instead.
Use 5/5/25/5 for idle ignition advance control.

Other than that.  Your VE table is not nearly tuned. You're using way too much ignition advance at 100 kPa and below for this engine. Your cranking enrichment table is realllly out there, also way too much cranking VE (150%). You should be fine using what's needed (from VE table) at 100 kPa full throttle in high gear and tune the enrichments from there.

[amd is the best]

It's overrun fuelcut. You can disable that, but it's not the root of the problem.

You should let the idle air control integral have much more power, +/- 20 isn't going to get you anywhere. Set decrease to 80-100 instead.
Use 5/5/25/5 for idle ignition advance control.

Other than that.  Your VE table is not nearly tuned. You're using way too much ignition advance at 100 kPa and below for this engine. Your cranking enrichment table is realllly out there, also way too much cranking VE (150%). You should be fine using what's needed (from VE table) at 100 kPa full throttle in high gear and tune the enrichments from there.

I want to thank you for your response first of all.  I really appreciate it.

I thought it was related to the fuel overrun and have tested a few different setings there but not much helped.  It's clear that my idle settings are off.  I'll do as you advise and change the integral decrease value from 20 to something in the range of 80-100 and change the ignition idle advance values to the above mentioned recommendations.

As for the VE table not being tuned, I'm not sure where you come to this conclusion.  This car has been running nearly a year and a half with it's current mapping that I created.  AFR's are spot on in the boost area.  What am I missing?  Also, is too much ignition advance a bad thing when there is no load?  What should the limit be and what are the consequences for having this too high?  I'll lower them down but how low should I go?  Closer to 30 acceptable?

The cranking enrichment table was not created by me, it came as a base file with my kit.  The car has started fairly well so I have not messed with it much.  What can you advise in order to bring it back in from "out there"? I'll set my cranking VE as you advise as well.

Thank you again,
Nick