So my jku with 20k miles is experiencing some major power loss. About six months ago I started running a flowmaster super 44. At some point I noticed my jeep wasn't making it up hills on the highway anymore in 5th gear. I just figured it had to do with backpressure and I really wasn't worried about it because I liked the sound of the exhaust. Well after driving 6 hours one way almost every other weekend now that school has started I decided to go back with the stock exhaust because downshifting from 5th, then 4th, and sometimes 3rd on the main highway was killing me. So after putting it back to stock it still won't make it up a hill on the highway in 5th or even 4th. It almost feels like it's running on the fuel saver mode all the time. Any thought as to what it could be? The check engine light came on so I'm going to be taking it to the dealer one day this week.