installed the pacesetter long tube header this weekend on my 97 4x4 aw4 xj. my observations:

-o2 placement is bad. it puts the o2 back by the trans and literally stands the sensor up into the trans lines once installed

-fitment lacks. once assembled, the downpipe etc was nowhere near its home. had to cut the piece with the trans mount and weld it back together *straight because the exhaust pointed up toward the floorboard too much to use the mount.

-the header comes with stepped washers. use them. they are a pain in the ***, but you need them. the intake manifold is thicker and requires use of these washers to seal everything up correctly.

-if you are anticipating gratuitous off-road use, i do not recommend this header. the front driveshaft is pretty close.

-the underside manifold bolts are much easier to access with this header.

it was easy to install the part itself. making it work with the rest of the jeep was the challenge. i am using all 2.5” exhaust and a ginormous muffler. it’s very quiet but noticeably makes more power. i’m very happy with the end result. as usual it took more time and money than it should have, but i’m happy. i bought the cheap painted header and had it coated locally. they did everything that came in the box. ill update in a few weeks with gas mileage info. it’s very easy to tell it has way more power. very responsive.

update - fiddled with the step washers and can’t get the header to seal 100%. i think it’s a combo of the dumb stepped washer idea and the header flange not being perfectly flat. i ordered a remflex gasket, should be here today. plans are to remove everything. going to mic the header flange and make the intake manifold match in thickness where the conical washers sit, so i can reuse the stock stuff. i think that both surfaces being the same thickness and a fat, soft gasket will solve my issue.

i must say, the exhaust leak sounds terrible but damn that header feels like it added 40 hp. it will be a nice sounding setup once it’s done and right. the mystery muffler is starting to open up a bit, it has a hollow, throaty sound like a flowmaster and it’s not one bit raspy.

the downpipe-cat connection is the one that needed attention. it’s a slip fit design. the crossover pipe was pointing up into the floorboard where the cat attaches to it. it is not a header install for the meek. it requires a lot of attention to be right. with any luck i’ll have the leaks at the cyl head taken care of by tomorrow night.

alrighty. time to update. pulled the intake & exhaust manifolds back off, replaced the felpro gasket with a fat, remflex soft one. ground down the intake manifold ears to match the header flange. i mic’d the difference. the intake manifold was anywhere from .125-.135 thicker than the header flange. i reused the factory conical washers. 100% leak free. finally. i don’t want to admit this but i bought a $6 box of muffler tape and wrapped it around the pinhole in the weld that was leaking. no leaks anywhere from the cyl head to the tailpipe. sounds good. like stock but throatier at idle. accel is very slightly louder and on the highway it sounds bone stock. love the setup. i included some pictures. remflex vs felpro and some of the grinder work.

update on fuel mileage for anyone interested. so far i’m averaging 18.5-19.5 mpg. which is exactly where it was before. this is almost all city, stop and go driving. i run 55 mph roads to work but i frequently stop at stoplights. i imagine it still gets about 22 on the highway, but i’ll know for sure after aug 11 as im taking a somewhat long highway trip that weekend. i reset the ecu this weekend to see if it makes a difference, but i imagine it will take another couple months of driving to get itself where it wants to be.

tldr: fuel mileage the same. power noticeably increased.