Not going to improve fuel mileage with any of those things. Shorty headers will be only thing that may give you some better performance.So Am finally going to put a cold air intake along with cat back exhaust. Been looking at the oem one an I like the look but in the $850 range not sue I want to spend that. So I looked at the S&B that the guy on Truck Central uses. Also looked at the EFE one witch spec wise pretty good. Anyone want to give some advice. Also looking at doing shorty headers of some kind. The normal cracked manifold and 6 to 7 month wait. May also do the pedal commander. Not looking to get a ton of horespower. Just improver MPG and some performance. I have a 2020 Limited with a 5.7 gas and 4x4. I had the oem stuff on my 2019 Larime 2WD which was 2 truck ago and loved the sound and feel. Also didn't mind the 22 MPG on the highway.
Might also want to check out Vararam for intakes.