Recently I leaned my map settings on my car using the Link, in hopes of getting better gas mileage, and I knew I was running rich. Now the car definately runs better, but my gas mileage went from 24mpg to 20 mpg based off of the last two tanks.

Why would my gas mileage go down when I lean the car??? I didn't lean all the mapps just the first three rows where the intake is under a vacume. Driving habits remain the same.