Gas Mileage and General Questions '03 V8

Hello. I have an '03 V8 Sport and have a few questions someone else may have already tried. I am thinking of getting the K & N air intake hoping it will increase miles per gallon. I see it adds horsepower but how does it affect MPG? I also wonder if it would void factory warranty if something were to go wrong?
I am also having a problem with the rear end 'bottoming out' on typical WV shuttle roads for paddling. The tire is hitting the plastic in the wheel well and eating it up. What would be the best way to prevent this without making the ride suffer? Was thinking of lifting it a few inches (not wanting it too noticeable), what would be the best way of doing this?

Thanks for any replies!!

Steve

IMO you will not feel any hp increase at the pedal. It will sound different and may appear to have more guts; but it takes a lot more money to actually increase the hp. It will not void the warrantee. And there is no bolt-on devise that will improve gas mileage.

I cannot answer your lift issue.

I have aT4R 03 Sport with the v8 as well