Depending on what the situation is where you live regarding emission inspection you can't get too creative when replacing /removing those two close coupled catalysts on the existing system.
if you don't have emission inspection, should be no worries except the cel light will be on all the time which would make me nuts because wouldn't know when another fault happens.
If you remove the cats and the cell is set and your IM program checks for the CEL, you will flunk.
if your IM program actually checks for the approved parts, you'll need those cats and you'll need approved cats$$$$$$

 

I live in Arizona so I should be good with the emission part right. Also if I get the y pipe with the O2 sensors will the cell still pop up. This is the pipe I’m thinking of getting, but I only see to spots for O2 sensors. It says it’s for a 2000 xj

 

How good are your mechanical and electrical skills? I run an 01 with a stroked 98 engine. Coil rail eliminator so I don't need the crappy 0331 head. Run a plain 98 exhaust but still have the rear "cat/resonator" at the transfer case.The 01 exh manifold with 2 cats is longer than the 98 so you have to weld in a longer downpipe segment that will reach. Also the primary 2 piece 00 exh manifold will not bolt up to anything but an 0331 I welded 2 bungs, one in each main pipe after the collectors in the primary exh manifold so O2 sensor 1 reads cyl 1-2-3 and the 2nd sensor reads cyl 4-5-6. After the cat/resonator i have a short pipe with 2 more bungs for the aft sensors in between resonator and muffler. I ran extender wires back to all O2 connectors as needed . I have NVER tripped a cat or sensor code in the 3 years since build. It might have cost me the same price as a complete 01 exh rebuild, but it was worthless to run a stroker thru the 0331 head i had an exh shop do the bung welding and pipe extensions. Its an option to keep in mind but obviously I can't guarantee the same results....i just REALLY hated that 0331 head. DISCLAIMER...I just realized that if your not replacing the 0331 head, all this is moot and your going to have to splurge for the y pipe and cats .Where do you live, you can have my old y pipe and cats but the bottom collector flange is rusted badly

 

I just thought of something.
Been a long time since I dealt with my exhaust on my '00.
I replaced everything from the dual cat back with Walker parts.
Now my '00 has a build date of 4/00.
But remembered that there is a cut off on the '00's for exhaust.
I want to say 1/21/00. When looking up the application for exhaust you are asked before or after that date.
Which means with your build date even though you have the dual cat your exhaust is all slip on.
Not flanges like mine.
So I am leaning towards that you want that cat you showed from RockAuto.
But I never really been able to determine what parts you want for an '00 with a manufacture date before 1/21/00.
So be careful what you buy.

 

So did you go with the walker y pipe from the pic above or by any chance do you know if they even makes y pipe like the factory one with 4 O2 sensors.

 

Mine is a CA emissions '00 and bought the Walker dual front cat.
But mine is a later date '00 has has flanges.
And instead of having that longer pipe like the RockAuto I needed to buy another pipe to go from the front cat to the rear cat.
By the way the 2 upstream O2 sensors are in the exhaust manifolds.

 

Oh I thought our parts were the same. I was going to ask you for the part number that you got. I’m in the pickle if I even should replace the y pipe. I want to just need to find the part.

 

Well that is just it.
I don't know cause of the year manufacture date cut off.
To this day I have never really been able to get a handle on it.
Never seen one up close and personal.
Only know what the computer at my Napa, I retired out of one, says when you look up the parts.
Look towards the bottom under Important Information.

https://www.napaonline.com/en/p/EXH5...ressionRank=20

They don't even show parts for before 1/21/00.
Does your front cat have a flange or is it slip on to the pipe after it?
Does your rear cat have flanges or is it slip on at both ends?

 

Idk if it had a flange connecting to the converter since it was stolen, but it was a long single pipe exactly like the rock auto one.

 

So leaning towards the slip on that I think it is.
Do you still have your rear cat?
Assuming not flanges and is slip on too.
With my exhaust everything is flanges and bolts together with the exception of the tail pipe to the back of the muffler.
I have the cat in the Napa link, that bolts to what we call the intermediate or down pipe, that bolts to the front of the rear cat, and the muffler bolts to the back of the rear cat.
Now just guessing here.
That extra length of pipe in the RockAuto cat has the intermediate/down pipe incorporated in it.
Which the end of that would slip into the front of your rear cat and go from there.
Thinking for your year manufacture that is the one you want.
Or one that looks like that from a different manufacturer.
But again please realize that I am just guessing here.
To this day I am always hoping I would come across one of these earlier manufacture '00's in the boneyard.
Just so I could see it up close and personal. Either confirm that I am right or just flat out wrong.
LOL.
So to confuse things even more.
While it would not be cheap I wonder if you could bolt an entire after 1/00 exhaust to an XJ with a manufacture date before 1/00.
This reason I mention this is because best I can tell there seems to be a lack of the exhaust parts for the ones dated before 1/00.
But I never really delved that much into see if they were or not either so.....
And to take it one step farther.
In boneyard one time I came across a Federal Emission manufactured after 1/00 XJ.
Now these just have the rear cat, using the Y pipe without the cats talked about in the beginning of the thread, and only 2 O2 sensors.
So I grabbed the PCM and one of the 2 engine bay wiring harnesses, the one with 2 connectors to the PCM and has the fuel injectors connectors on it, thinking maybe someday
I might convert my CA Emissions '00 to a Federal Emissions '00.

 

My rear cat was stolen. Can I just switch it with parts like yours with flanges, I’m pretty much changing everything manifold to tailpipe.

 

That is kind of why I brought it up.
But like I said I don't know.
I don't see why not but.......
Maybe they had old parts that they wanted to use up before they went to the way after 1/20 is set up.
Maybe they figured the flanges are better from a manufacturing point of view.
Etc,
My buddy always says they don't design cars to work but to make them easier to build.
I just don't know.

 

I found thei sheet online to find the part there different numbers idk what they mean. My test group name ends in 130

 

Sadly im losing the flow of the thread, but in a response to your question of the upper o2 sensors in the post with the picture of he davico cat segments...the upper o2 sensor bungs are in the upper exh manifolds...then the cat segments bolt into the manifolds and now you have 4 sensor ports. My 01 cat segment ended in a flange that would bolt up to the flange on the downpipe. The ones in the picture appear to be one piece all the way to the aft cat. Pick a easy spot to cut and connect.