I wanted to check , Amsoil Ea , airfilter .

[JFaughn]

I put an Amsoil Ea filter in the truck almost a yr ago , the 1st reason for testing is , my millage has gone up & down , in the last yr , many possibilities , the changes in fuel ? #2 - winter , summer , LSD , ULSD , methanol bio , ethanol bio .
I expected to drop the beginning of winter last yr , then spring came , the warm weather fuel [ no #1 ] fuel millage did not come back up for a month or so after , then about 2 mths ago it dropped again .
I've been using bio & a couple varieties [ methanol processed bio & ethanol processed bio ] on average about 25-28% , the last drop was about the time I started with the ethanol bio .
Finely to the air filter ?? in trying to nail down whats , what , I thought to test airfilter , I've got a piece of 4" exhaust between filter I factory intake hose , no airbox .
I drilled for a vacume fitting in that piece , ran the gauge into the cab , and I can not get the gauge to move , haven't not cleaned the filter , but its not thick with stuff , so my thought was that I would see at lest a little wiggle , none .
So the ? is where would you put a fitting to see if the filter was restricting ?
Thanks John