Decreased gas mileage with new exhaust...help

[jfw432]

I originally bought the K&N cone filter for my Jeep and that gave me 1-2 extra mpg. I then bought a high flow catalytic converter and a free flow muffler and that dropped my gas mileage 3-4 mpg. Everything I've ever read says a less restrictive exhaust gets you better gas mileage. I noticed performance gains with the K&N filter but nothing or little change with the new exhaust.

I checked the ECU and got no code readouts so I assume that all of the sensors are good. I've had the exhaust for 3-4 months at least and reset the computer when I did get it.

The sound of the exhaust is really loud at 1500 rpms and when I'm hard on the throttle. Hard on the throttle I consider normal but the low rpms noise gets me and I don't understand it. Could there be a leak somewhere that is causing a problem? Would a small leak cause the huge decrease in gas mileage as well?

Any help or recommendations are appreciated because I'm stumped and the low gas mileage is killing me.

[Dsilver]

That's really weird man, yeah usually upgrades like that increase power and gas mileage, because they make the airflow through the engine more efficient etc... did you get your exhaust and stuff installed somewhere or did you do it yourself because maybe something is loose and your losing pressure somewhere or something I dont really know.

[4.6chickenpower]

could it be that you are giving the jeep the same amount of gas as you did before the mods, it could be that you are not used to the power gains