1993 Cherokee XJ 4.0 I6 2wd Ax15

Okay, so my DD is a 93 XJ 4.0 I6 2wd Ax15. Im not looking to do any wheeling with this one, would like to learn the ins and outs of this baby first.
Im finishing up replacing the throwout bearing, clutch, and flywheel at this point. Was fairly simple, wouldnt mind having to do it again.
I would really appreciate some educated input on some aftermarket mods.
I want to increase gas mileage, I believe the stock comes with 3.55 gears, however I have little get-up-n-go power. What new gear set should I get?
Im also looking for aftermarket long tube headers, any favorites?
I read about a 2.5"X8" Stainless Flex piece to relieve stress, however I'm somewhat familiar w/ stainless and couldnt see it holding its own in a corrosive atmosphere.
Also curious about hood scoop intakes, dont mind having to hire a fabricator/welder.

Any advice you folks could give would be greatly appreciated.

are you shure you dont have 3.07 gears? most 5 speeds came with 3.07's. in my experience with after market mods heres what i have found. headers do nothing for 4.0's, i had a gibson and did not notice any difference. cold air intakes help throttle response and maybe 1 mpg. a freer flowing muffler helps a little bit. honestly put some 235 tires on it, fix all the oil leaks, and change the fluids. i use to have a 91 four wheel drive with a 5 speed and 235's i got 21 mpg on the highway

With the AX-15, you should have a 3.07 ratio in your axle. Autos came with 3.55 for the most part. So if you wanted to, you could switch out to a stock axle from an auto for a little more pep. (3.55 with 33" tires is also the equivalent to your 3.07's with stock size tires BTW). While your at it, look for a Chrysler 8.25 instead of a Dana35. Much more stout axle if you plan on driving hard or going with a larger tire.

As far as the scoop goes, I think it would be pretty tough to fab something up centered because of tight clearances between the valve cover and the hood. You may be better off going with a set of hood vents or louvers to dissipate some heat out. Also check into http://naxja.org/forum/showthread.php?t=1006537 . Yella was running a snorkel when he picked up the blue rig, but thought it looked bad, so he designed a vent/intake system using a vent from a marine supply store that scavenges cold air from inside the fender area and takes it into the rear of the stock airbox(as apposed to the front like the factory designed them). Not a bad option if you dont mind hacking a hole in your fender! Good luck!!!