Warped surfaces are a possibility - it is a VW after all.
I would take it apart there first ..see what is going on ,
and either replace the gasket there, or reseal it.
   I usually use Permatex High Tack as a sealant in that area.
or The Right Stuff sometimes .
Look for cracks too.
Generally speaking ....on all sealing surfaces that get tightened ..
and sometimes re-tightened, often for years..the surfaces warp some
eventually.
  Sometimes the repair is a better used part, or filing something very
flat ..
or even hand lapping a surface to new flatness with valve grinding
compound on a plate of thick glass.
   A magnifying glass or microscope even,  for inspection, is not
inappropriate at times.

I've found up to a dozen tiny air leaks between throttle plate and
intake ports on vanagon engines.

though this one leak may not be 'the reason' for your emissions test
failure ..
but it sure is something that should be fixed in any case.

Scott

On 7/18/2012 1:05 PM, Ken Wyatt wrote:
> Greetings Vanagonauts,
>
> I've been having trouble meeting the hydrocarbon standard on my AFC
> 2.0 l aircooled engine here in Salt Lake City, UT.  Its a fairly new
> engine with only about 6000 miles.  It's hydrocarbon output is about 4
> times higher than it should be at 800 ppm instead of 220 ppm or
> lower.,  The emission guy said he thought it was a vacuum leak near
> the right head looking forward. (He sprayed carb cleaner around the
> engine I guess)   So in my efforts to achieve emission compliance, I
> have isolated a slight vacuum leak at the #4 intake manifold right at
> the cylinder head.   It revs slightly when I hit it with starting
> fluid.  I tried to simply tighten the intake manifold bolts a bit but
> that didn't do the trick. I'm wondering if others have had such a leak
> and would new gaskets likely solve this issue or is it perhaps more
> complicated than it appears like as warped head or something.
>
> Thought??
> TIA
> Cheers
> Ken Wyatt
> 82 westy
> SLC, Utah
> (where emission stds rival CA I think!)
>