I've been running it for several years, can't say if it increased power but when I 1st had it installed it did seem to have a bit more oomph.
in comparison to the stock system and having traveled the same route with both on I-70, I have to say it does feel like I have a bit more mid-range power than before but nothing that'll make you go wow...it seems to hold in the powerband a bit longer for a nice steady climb.
it has no drone which was my #1 when looking at it but it does sound good when it opens up. it is tucked up better than the stock muffler.
I've been happy with it, I get ok mileage for a Jeep - but it's not all from just the muffler. I have a CAI but I'm beginning to think the stock air cleaner gave better performance. I'm hoping to install the stock air cleaner this weekend to see it makes any difference.
I also bought a Dynomax Evolution ultra flow it was at such a good price, I'm just hoping the performance outweighs the drone lol