Hi,

Just my 2cents, but I recently bought a Purolator air filter for $8 at
Pep Boys for my 87 van.  A lot depends on the conditions you drive in. 
For standard driving, you probably don't need the heavy duty.  On the
other hand, if you drive a lot on dirt roads, or under other such
conditions, you may consider it--but will it last 4 times as long as the
standard?  It would have to to make up the cost difference.  The K&N
would need to last a little over twice as long.

Tonya
87 Vanagon GL Wolfs
74 S. Beetle