Hello,

I too used the 10% ethanol blend (mostly ARCO) in my '84 without a problem 
until:

A couple of years ago, while traveling in Idaho during an exceptionally hot 
spell I started getting vapor lock type problems.  I took the car to a VW 
dealer and was told that a lot of Vanagons were coming in with similar 
problems just then, and that there was a free factory authorized fix.  I had 
it done and no further problems.

The fix as described to me:  It seems that excess fuel not needed at the 
engine is returned to the fuel pump at the tank.  The circuit is such that 
in the header just below the tank the gas from the tank and the returned 
fuel join and flow into the pump.  The vapor lock condition occurs when the 
loop gets a vapor bubble in it that ends up in the pump.  The free fix was 
to drill a second hole in the tank header leading to the tank.  This allows 
any vapor bubbles in the fuel return path to rise through one tank path and 
be replaced by gas through the other tank path.  The fix took 15 minutes at 
the dealer, but I didn't see them do it.  I have never had the problem 
again.

As a side note, I live in Phoenix where the summer temperatures are almost 
indescribable.  The local gas suppliers do not use gasahol in the summer and 
avoid the high vapor pressure problems.

Mike