In the market for replacing my stock exhaust on my 4.0 with 142,xxx miles. Done quite a bit of research and see that a lot of people are doing cat back systems verses header back kits. My question is, if your replacing everything from your cat back why wouldn't you go ahead and get a new header and cat as well? I know there's a significant price difference but it just seems like it it would make more sense to do it all while your down there. I'm not looking for more of a rumble its just very old and rusty and I figure a complete exhaust replacement will help with performance and allow it to breath a little better. Advice please as I'm purchasing soon and don't know which route to take.