The recent discussion about possible improvements to the intake air flow
chain in the vanagon got me to thinking.
Here are my theoretical assumptions:

1. The volume of air required by a gasoline engine is directly proportional
to RPM.
The higher the RPM, the more air needed.  A gasoline engine needs to
maintain a relatively constant air fuel ratio.

2. The stock air filter - throttle body - intake manifold  system is capable
of flowing enough air for the stock engine up to redline.

So, increasing the volume of air the intake tract can flow will have no
affect on power or fuel economy (in a stock unmodified engine).

If you drive your van at less than redline, increasing the size of the
throttle body and/or increasing the size of the intake tract will have no
affect
on performance.  Certainly everyday city driving is far below redline, well
within the capacity of the stock AFM and air filter.  Even if the stock
system is
restrictive, there should be lots of headroom for normal driving with a
stock engine.

If you do not accept the above, then some related questions are:
- just how bad is the stock system?
- do things like K/N air filters really honestly offer more hp and better
mileage?

Corrections and rebuttals welcome.

Gary Lee
Calgary