There are numerous write-ups on curing a lumpy or incorrect idle in a
Vanagon. My Westy idled like a small wash machine.  Ok, not that bad, but
you get an idea.

Things I checked:

1. Spark plugs - replaced with my favorite Bosh platinum +4. Runs good, but
no difference in idle.
2. Cleaned ALL the grounds when I installed my DJ-code WBX, so that was not
the problem.
3. Checked for vacuum leaks by spraying various vacuum lines and intake
areas with carb cleaner. I found a tiny leak at the base of the idle control
valve. No change after fixing that.
4. Timing was spot-on at 10 BTDC as per DJ-code spec, with a total of 40
degrees advance.

I happen to get a set of fairly new injectors off of an '89 Vanagon. I put
them on while my wife was making dinner. It didn't take long since I had the
whole assembly with brand new fuel lines and good fuel distributors.

BINGO! She now hums along happily and runs more smoothly too.

BUT... when I tried to set the idle I noticed after plugging the idle
control unit the idle went up about 150 rpm. EH? I had a spare ISV laying
around. I cleaned it and put it on.

BINGO! The idle now stays put. The write-ups mention the ISV, but the one I
replaced moved freely and hummed like it should. The problem was that it
bypassed vacuum when fully closed.

So, there you have it. Just one more thing to add to your rough-idle
checklist, the injectors.

--
Chris S.
Disclaimer: "Death and serious injury may occur"