Well, maybe not the best analogy.  Several times over the last 6 months 
my '81 Vanagon (159K, new heads 100K) has experienced what appears to be 
a loss of compression in one cylinder with an acompanying "phrbttttt" 
sound (similar to using a compression release on a big single motorcycle).

Very unnerving.

After stopping and sitting for a while, the Bus returns to normal operation.

Any ideas?  Could this be a fuel delivery problem?

Bob Hufford
Transporter Search & Rescue
bhufford@mail.orion.org