Engines make various amounts of mechanical clatter, but most of what you
hear is the combustion.  You hear it from 2 sources, the exhaust (obvious)
and the intake (not so obvious).
  We have tried several intake arrangements, and probably a few dozen
combos of exhaust components.  We are going to stick with our intake for
the foreseeable future as it is dead quiet, utilizing all Subaru parts.
The exhaust components we are using are mostly stock Vanagon, not
including the Smallcar headers.  We are also offering a "performance
exhaust" with larger muffler, cat and tubing, with similar noise levels.
The exhaust note you heard this weekend was all stock Vanagon exhaust. It
sounds very much like a WBXer driving, albeit much quieter at idle.  You
can barely hear it in a Westy at 65-70 mph.
   All Subaru van conversions don't sound the same as they don't all
utilize the same intake and exhaust configurations.
   People love their vanagons, so we are trying to maintain our 4 cylinder
Subaru conversions as "Vanagon-like" as possible. The extra 70 hp, better
MPG and reliability are bonuses. It even looks stock from the outside.
   The engine that was in the silver Westy at Everybus was installed hours
before Hans drove it to Everybus.  I have done similarly quick trips to
Chicago and FL right after installing a Subaru.  We put em in, drive
them,and forget about them. They very quickly seem "normal."

   John
   East Coast Vanagon