I do believe it only has one, but please correct me if I am wrong.

 

Yes there's two. Hi Flow cats will be a benefit.

 

2 cats, and not so sure the highflow cats will give you your desired gains, at least not N/A same with the long tube headers. These really shine when you have a supercharger or turbo.

Loosing too much back pressure can be a bad thing on the 4.0! I had the dual exhaust kit from NTO on my 2010 4.0 and ran great with the JLT CAI & SCT tune in 93 race, a friend gave me MAC axlebacks so I installed them and they sounded great at idle(like a GT) the drone was horrible and the loss of back pressure was not a good thing, the car was really bogged down performance wise, as if I had 1,000 pounds in the trunk. I put the GT Takeoffs back on a day later and never looked back.

 

I wonder if anyone has actually tested the "back pressure" theory on a dyno, and at the 1/4 mile. I would love to see the results of the high flow axlebacks vs the more restrictive (but still better than stock) ones.

 

+1 I'm doubting high flows will be that beneficial. You might feel a slight "ass dyno increase" that you're making up in your head. I would suggest gears if you don't have them yet.