Norman Leong wrote about the ad he encountered "MSDS Clean Air Act"  
available for '84-up Vanagons, which included the following claim:
* Up to 8 hp increase
to which I can only say that if people are going to tell tales like this 
claim of adding 8 hp to a standard Vanagon, they should at least keep the 
claims within the range of possibility.  I've spent enough time around 
flow benches and dynos to know this.  Even running tuned length, 
turbulent free straight unfiltered induction probably would net well 
under half this 8 hp increase.

  No need for simply applying "Standard disclaimers" in my opinion.  A 
good stock air induction path does not sacrifice 8 hp on a factory 
Vanagon.
     John