checking air filters

[davidkerryedwards]

How do people test their air filters? My European Mercedes motorhome had a
nifty feature.
It had a vacuum operated piston in the intake. When the air filter go dirty and
vacuum
increased in the intake, it would suck the piston down and it would show red in
a little
window. I see my intake, pre-turbo has a schrader valve (inoperable) in it
which I assume is
for testing with a vacuum gauge. Do other people have that? If not, what are
the options?
With filters at $80 it's nice to have a test before replacing.

Kerry
82 FC 35
Denver