Hi Steve,
     I would check the o2 sensor,the temperature 2 sensor and the afm (air
flow meter).   The engine will naturally have a little richer burn at higher
altitude but the o2 sensor should alert the ecu to that fact it sees a rich
mixture and the ecu should correct the mixture. If there is a problem with
one of the above mentioned sensors and primarily the afm the ecu will not be
able to correct enough to the lean side and the engine will run too rich.
Attach a lcd meter to the o2 output and ground using a long wire,  watch the
o2 voltage. When all is good it will bouncing above and below 0.5 volts,
when rich it will be above 0.5 volts and when lean it will be below 0.5
volts. The reason I suspect the afm is the ecu will only correct the mixture
up to a point and then it is programmed to ignore o2 because its output is
assumed to be wrong and the system goes into open loop.  I had a very good
lesson in this scenario last year at bbta (busses by the arch) in STL .  A
party there had a afm set to the rich side, his ecu ( an early bosch) would
not correct the mixture. I plugged my spare ecu (a triumph adler) and all
was good. His ecu was ok in several other vans there.  After we determined
his van was very rich in open loop ( ecu uses temperature and afm sensor but
not the o2 sensor). We corrected the rich running by adjusting the afm main
spring for a proper mixture in open loop and all was good with his own ecu.
Sorry this got so long thanks for hanging around and good luck with your
quest.
Darrell

----- Original Message -----
From: Steve Folio <sfolio@SIMCO.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Tuesday, June 22, 1999 1:05 PM
Subject: huge loss of power

> 86 Westy GL has problems at altitude (5000+). It will slug and loose
> power drastically.  It almost feels like bad gas (the VW, not me).
> Running fine at sea level except for a noisy water pump. Any thoughts
> would help out.
>
> Thanks
>
> Steve Folio
> 86 Westfalia GL
>