Hey guys, brand new here so please be gentle.

Recently I have been given a VERY clean 1996 Jeep XJ (dark blue/dark blue pearl? will send pics if people wanna see it in the future) from someone in my family. He recently passed but randomly left it to me based off a comment I made way back in the day about it being a cool little thing. I had NO idea how crazy and passionate people were about these XJs, and after doing some research and seeing how satisfied people are with them, ive decided that im gonna be giving it some TLC and fixing it up a bit. Its not in bad shape at all but im sure some of the common problems with it are some of the same problems I can see swelling up. Its only got 100k on it, original owner too and he kept it in great shape.

My question is this, im going to be putting in some money whenever I can on this thing, and the first thing im going to do is try to get some more power and MPG in this 4.0 mighty mouse beast. What would be the best approach (products) to get for the full exhaust system? I know my way around a honda (a little bit) but ill be the first to admit I have no idea what I should be looking for in a jeep. So what would a full exhaust replacement be like? Headers/cat/pipe/muffler? or is it a little more nuanced than that. Im a noob, so again. be gentle. Help and any recommendations would be appreciated, if you guys have the time. If not, no worries. Have a good day everyone.