'89 200TQ Decceleration cut-off valve, OXS sensor

[e6941tb@ix.netcom.com]

Hello!

I have just replaced air and fuel filters and the OXS sensor, after
which ran a test by Bentley.
Here are some results:

On the Decceleration cut-off valve:
1. A voltmeter is hooked up in parallel to the Cut-off Valve connector,
which remains pluged in.
2. The RPMs are risen above 2000 after which the throttle is released,
slamming shut.
3. The meter reads 90mv (~0v as far as this test goes), although should
read 12v.
4. Idle switch checks OK.

based on §§1-4 Bentley concludes: replace Decceleration Valve Control
Unit.
Before I do that, anyone BTDT?
Given the horrendous appetite of my red Q (15mpg city), this may very
well be the case. Maybe the fuel is not being cut off when I brake with
the engine.


Also,
On the OXS sensor:
1. My Wavetek multimeter is connected to the OXS test connector, i.e.
"common"(black lead of the meter) to brown and "V/f/%"(red lead of the
meter) to double Blk/Blu.
2. The connector of the Decceleration cut-off valve is unplugged. The
terminal 2 of the harness side of this connector is jumped to chassis
ground.
3. The meter should read 40% duty cycle steady regardless of the engine
speed.
4. In reality the meter reads 60% steady regardless of the engine speed.

Is it possible that I am reading the same duty cycle, only my meter's
aquisition occures on the rising front, whereas the VAG factory test
device uses the falling front or vise versa (60%=100%-40%). 
I hooked up my Techtronix scope, expecting to see a nicely shaped
rectangular wave - no such luck.
The graph looks rather funky, with sharp spikes superimposing the
rectangles (perhaps some strobing impulses).

Am I chasing my own tail?
Any ideas from our esteemed turbo/computer gurus?
TIA

Igor Kessel
'89 200TQ