Something like this?
Winner, winner, chicken dinner.....
As far as back pressure is concerned, slight back pressure down low helps with low end torque. Of course, removing a stock restrictive single pipe and replacing it with headers will show larger gains as will replacing it with a solid dual exhaust with the right size tailpipe. In that case however, most notable
gains with the headers will be in the upper end and will be dependent on other upgrades as well.
Dual exhausts are routinely connected via a crossover pipe (or X pipe) to help smooth pulses and equalize the pipes, which helps scavenging. Unfortunately, Jeeps have a limited amount of room underneath, which forces many of these upgrades, which are routinely found on cars, out of the picture.
On cars, headers last much longer, and have fewer problems. However, Jeeps routinely experience a lot of twist and flex, as well as vibration, extremes of hot and cold, rock strikes, broken hangers, and a plethora of other stresses not seen on street cars. These generally add up to more problems and a shortened header life.
I run headers on my CJ, but it is because it is about the only way to effectively route the exhaust and allow for the
Saginaw steering upgrade. I have been through two sets and if it were cheap and easy, I would return to stock manifolds in a heart beat.
In the end, there are just as many folks running headers as there are manifolds. Both sides (that are happy with their setup) will argue their point. That is the nature of a forum. To get opposing sides of modification. No reason for anybody to get excited or take anything personally. If the OP decides to go with headers, well, good for him. I wish him the best of luck......