After changing my diff fluid transmission fluid, and cleaning an re-oiling my K&N filter, my fuel mileage went down from 23mpg to 19.5mpg.

I was looking at my airbox, pulled it out and found this hole at the bottom. I was wondering is there something that should be connected to this hole? Just seems strange to me.

 

Yes, it should connect to plastic black box which is a resonator. If the box isn't there, the prior owner of the car likely had some sort of CAI installed and removed the box. I've found that the resonator really doesn't reduce sound, but rather improve lower rpm throttle response.

 

Thanks for the info, There is no box there, so that's probably not a good thing. I can't believe I've been driving my G for a couple years an never knew