I have a different style aFe stage 2 also. I like it. Really just sounds good. If you don't like loud then don't go WOT! Sounds like a jet. haha
No reports of "MPG or HP" gain. Maybe some throttle sensitivity at first (expected) or maybe just in my head.
Make sure when you buy or get the cleaning kit..that it's the right one with the right part numbers for your filter. They send me the wrong oil for my oiled one and it effed it up so I bought a dry filter. Went mudding and it got a little dirty and cant get it perfectly clean. Now my truck sounds like I have a turbo because it whistles