After air filter change 2004 Honda Pilot mileage reduced by 50%

[Bobbio]

After air filter change our 2004 Honda Pilot mileage was reduced by 50% (got about 11 mpg on interstate and we used to get 24 mpg). I checked tire pressure and they were low, so I inflated them. I have a code reader, and the car is showing no error codes.

I am looking for advice/ideas.

[Tester]

If you replaced the air filter the air box cover had to be removed.

Check to see if a sensor got unplugged or if an air leak was created between the air box and the throttle body.

Tester

[MikeInNH]

How are you calculating your gas mileage???