Exhaust question

Hi all. First post here so be easy on me... First let me say this is a wonderful site. I've used the search feature and cured my rear brake issue, and will get the backup lighs working soon...lol Oh, i have a 98 Cherokee Classic inherited from the wife who now drives a new Honda Civic.

I have 146,000 miles on it. The Jeep drives great and i have been very meticulous with maintennance. Right now the catalytic converter is rattling with loose stuff inside....it needs to be replaced. The muffler and tail pipe appear to be ok but i wonder with that many miles. I've read that doing a cat back r/r with 2.5 inch exhaust will net 6-10 HP.

Since I am going to have the cat replaced, does it make sense to do the rest for the performance increase? Will my mileage get any better?

Also, should the O2 sensors be replaced? The rascal seems to drive well with ~20 MPG.

thanks,
Greg

from what i gather there wont be a noticable difference in doing just a catback. you have to do a high flow intake, bored throttle body, header and all that stuff to get a noticable difference in gas milage or power

My cat back freed up a few HP and 1/2 MPG. Plus it sounds great. I got the System from Rusty's Offroad and it bolted right on. Adding a bored throttle body and a K&N also helped add HP and another 1/3 MPG.

I was always told that exhaust mods come first and then move on to the intake mods.

If you are getting 20mpg I wouldn't touch a thing until it fails emissions.

I would not bother with O2 sensors if they're not throwing codes or messing up your mileage. For the exhaust, I'd determine that partly on the basis of what's there. The original Jeep exhaust was pretty decent, but some aftermarket mufflers have a slightly smaller bore, despite being sold as an exact replacement, and my seat-of-pants dynamometer says they steal a couple of horses. If your exhaust is in a single piece, right back to the tailpipe, and if you can see the Mopar star on it, I'd let it be until it rots. If it's more than one piece, you might consider replacing it with one that's known to be correct.