Problem - realtime MPG needs recalibration after intake mod?

[Showerbabies]

My 2007 5.7L CM has the charcoal screen removed, and the box is cracked open.

During the first hours of delivery, I noticed the realtime gauge was pretty accurate b/c I was getting high teens/ twenties on light throttle.

After cracking open the box and removing the screen, I noticed I get BETWEEN TWO and TEN MPGS, on light throttle, and between 0 - 30mph!!! WTF!?

I thought the ecu needed to be reset, so I pulled the fuse and disconnected the battery. No luck afterwards. I then closed the box back up, and yet no results.

Ideas? Am I really getting roughly FIVE mpgs on light throttle? I baby that sucker and it shows average MPG of 15.6.