On Feb 19, 2011, at 5:12 PM, John Goubeaux wrote:

> I'm on the road and several hundred miles from home ( southern CA) and
> my 90 Vanagon has begun to run bad. It is missing and has a serious
> reduction of power when under load. It starts up and idles, but is
> running real rough, no backfiring though. Its almost as if there is a
> fouled plug or bad ignition on one of the cylinders

Wondering if this is what you have going on:
""Condition: After driving for an extended period of time at a constant speed, the vehicle may, on occasion, experience a deterioration of performance which may be accompanied by hesitation or surging. In many cases, after turning off the engine and subsequent re-start without having taken any action, the symptoms disappear. These symptoms may not recur for several weeks or months."

"Service: To resolve this condition, wire harness Part No. 025 906 302, should be installed. This harness provides improved signal voltage stability."

Remove electrical connector from air flow sensor. Install wire harness, Part No. 025 906 302, between main harness connector and air flow sensor connector.

Part numbers are for reference only. Always check with dealer for latest parts information. As of 6/1/98, it was still a good number with list price of $138. VW calls it a "transformer" and the technical bulletin does indicate there are "active components" in the harness, so the old manual's trouble shooting resistance of the circuit are no longer valid. They are given in the bulletin.

To test the new harness, continuity between ends readings should be: #1, 0 ohms; #2 greater than 1 megaohms; #3, 4 & 5, 0 ohms."