First, let me apologize for the sin of forgetting a subject line.

Thanks be to all who have replied, but I am not really looking for direct 
diagnostic help. I am familiar with the "cleaned off" spark plug - BTDT, but 
there is no evidence there. I am not driving beasty to anywhere, so no mechanic 
for a sniffer. And the single biggest scalp-scratcher of all, there is no 
tell-tale smoke from the exhaust. Nor any smell. Those were my first thoughts, 
and first checks, there by the road-side. 

Is there an odd Vanagon, WBX-only way to get this symptom set? That may not 
involve a crack in the head? The cooling system seems convoluted enough...

What else will give me air?

I am going to try the reverse route, and put pressure in the cooling system, and 
see if I can find were it goes...
�Evan Mac Donald 

"...in the absence of facts, myth rushes in, the kudzu of history."
-Stacy Schiff