Greetings again. Along with startup surges, new challenges.
 My idle is doing strange things. Has a shudder in it, kinda shakes the
van, then smooths outs for a bit. Almost like a miss in the firing.
Worse when it is has been running for awhile. When you turn off the
motor it shudders, almost like it wants to run on, but doesn't. Same if
you start up and the motor is warm. Starts with a shudder. And then I
have these vibrations ( driveshaft is out )which are most noticable at
3000 rpm, and especially 4000 rpm. Almost like a double vibration. Also
pronounced when de-accelerating at the same points in the rpm band, but
includes 2600 rpm. Usually pretty smooth over a 100 km per/h, although
there have been times when it feels rough. Just returned from a 600 km
day trip and half the trip the motor felt rough, and then like a switch,
it smoothed right out for the other half of the trip.
I have checked and replaced numerous parts as mentioned in previous
postings. Other checks have been made: tranny & motor mounts. Tranny
mounts are fine, but hard to tell on motor, but they appear fine. The
vibrations don't feel anything like CV's. Those I have felt before.
Took the van in to a local VW dealer and had the timing, mixture, etc.
done on their equipment. 02 sensor working fine, CO set within limits,
timing right on, but the HC'S were high. 400%. Could not bring it down.
The technician was also concerned with this, so he did a compression
test. 130,145,145,165. Possibly a case of carbon build up. Injected fuel
soaking up in the carbon at startup. Lots of unspent fuel. Tried
decarbonizing, then a crankcase purge. That helped a noisy lifter and
changed the compression readings. Now at 145,175,175,150. In the end,
not much changed, a bit smoother. Also of note, mileage seems ok in city
and hwy., but long hwy  drives leave a blackened tail pipe. Tail pipe
remains clean in city driving.
Maybe I need a leakdown test to determine more. It was suggested that
cam lobes could be be worn, sticking or an unseated valve.
Has anyone on the list experienced similiar problems? Does this sound
like a mechanical problem, or an FI problem?
Thanks for taking the time to read this.
Randy