cis-e operation with going/bad o2 sensor

[amalventano at sc.rr.com (Allyn)]

this is on the passat, but its still the same cis-e so it applies to 
basically all of us with 16vs.

just wanted to bounce this off of the list to make sure im not off on my 
diagnosis.

symptoms:
- low power while driving (no misses, just not as much power as there should 
be)
- at idle:
-- idle speed constant, but engine stumbles slightly every 4-5 seconds, then 
recovers
-- noticable smell of fuel
-- dpr current fluctuating at ~6mA +/- 1mA (fluctuations follow stumbling)
-- o2 sensor voltage fluctuating between 0.2 to 0.8 VDC (also follows 
stumbling, and fluctuates more than i normally see)
-- manual adjustments of sensor plate, bringing DPR to various readings 
(3mA, 10mA, 15mA), all yield the same symptoms (stumbles, fuel smell), once 
DPR stabilizes.
-- manual adjustment of sensor plate beyond the DPR range (adjusted 1/2 turn 
beyond hitting the stop at ~16.5mA) yields smooth idle and no fuel smell. 
(for those not DPR savy, this action forces the management to run a tad 
leaner than it wants to based on o2 sensor feedback alone).

i think its the o2 sensor. while its still functioning, it appears that the 
voltage is lagging behind what is actually going on with the exhaust gasses, 
causing the management to hunt excessively.

have i missed anything obvious here? any other checks i should do before 
ordering a replacement o2 sensor?

thx in advance for assist.
Al

Allyn Malventano, ETC(SS), USN
87 Rieger Scirocco GTO 2.0 16v (daily driver, 200k, rocco #6)
86 Kamei Twin 16V Turbo Scirocco GTX (33.3% complete, rocco #7)
86.5 Occo 16v Trailer (rocco #8)
90 Passat GL 16V (the wifes new daily, 200k)