2000-2001 exhaust system questions

I finally have money thanks in part to the federal government (damn taxes!). I want to upgrade my exhaust, possibly manifold back, but the exhaust on 2000-newer 4.0's is much different than earlier years. My exhaust has:
-2 cast iron manifolds (split down the middle)
-2 O2 sensors on the collectors
-2 pre cats
-2 more 02 sensors after the pre-cats

then the downpipe and all that jazz. There are no 02 sensors near the main cat at all. I have found most places say that their cat-back exhausts are 84-99, and will not fit my 2001. What gives? Has anybody replaced their 2001 exhaust (partial or full fledge) and lived to tell about it? My downpipe is 2.5", and the cat back is 2.25". I am looking at a catco 2.5" highflow cat, and probably a 50 series flowmaster with mandrel bent pipes, but what about up top? Info please! Help me spend my money!
-Jonnyd

My 2000 had 3 cats too. I ran a '97 manifold and "under car" cat. I plumbed the 2 upstream O2's into the front of the cat and the two downstream o2's after the cat. Works great, no codes. MIKE

check out my reply to the thread "specific exhaust question" I have a 2001 and I am very satisfied with the exhaust I purchased form [email protected] I am very picky about my Jeep and didnt have one complaint about anything on this exhaust the price is very good 2 .the guys name is Nick Ianuzzi, phone number is 480-998-3661, do yourself a favor and call this guy You Won't Be Dissapointed

JONNYD said:

I finally have money thanks in part to the federal government (damn taxes!). I want to upgrade my exhaust, possibly manifold back, but the exhaust on 2000-newer 4.0's is much different than earlier years. My exhaust has:
-2 cast iron manifolds (split down the middle)
-2 O2 sensors on the collectors
-2 pre cats
-2 more 02 sensors after the pre-cats

then the downpipe and all that jazz. There are no 02 sensors near the main cat at all. I have found most places say that their cat-back exhausts are 84-99, and will not fit my 2001. What gives? Has anybody replaced their 2001 exhaust (partial or full fledge) and lived to tell about it? My downpipe is 2.5", and the cat back is 2.25". I am looking at a catco 2.5" highflow cat, and probably a 50 series flowmaster with mandrel bent pipes, but what about up top? Info please! Help me spend my money!
-Jonnyd

Click to expand...

I have excellent results from this and install was super simple:
http://www.gibsonperformance.com/products.asp?pid=14297&make=32#parts

That looks cat-back to me. He wants to lose the 3 cats. (I think. At least the 2 pre-cats). Gibson doesn't list headers after '99. You can use any '91-'99 header and cat, just weld the bungs in as I said. It works. And has for 70,000 mi, no codes. And passed emissions. And the mirror check (They don't know what they are looking at. They see a cat. Didn't notice all of the extra wires. ) I had to lengthen the wires. I put the extra bungs on the top of the cat. A little close to the floor, but, harder to see/hit. I used a stock '97 exhaust. It bolted up. Any aftermarket stuff should too. I used the '00's sensors. I did it because the cast iron/cats wouldn't clear the blower manifold. If you wanted a header, you could do it the same way. MIKE
PS. Depending on states, some have the CI manifolds and one cat (I've seen them). Mine was a Cali LEV model (bought from a PA dealership ???). These have 3. A "one-cat" y-pipe should be available from the dealership. If all you wanted to do was lose the pre-cats.

I would'nt worry about the two precats, they cause trivial restriction. I have a Banks header and would recommend it very highly. No fabrication to install, it is a direct fit. to your precats and downpipe. Speaking of the downpipe, DO NOT get rid of that. It's perfect at 2.5"

They really changed that much between 98 and 2K ? THREE cats, man, here I thought 2 O2 sensors were overkill on my 98....

Yea Rich I think they added the pre cats mid year 2000 [mine dosn,t have them]. They also went to a distributerless coil on plug iginition supposed to be as good as a hot coil, good wires,and good cap.

Thanks for the info guys. Ya, 4 o2 sensors are a bit much. For now i am going to go with just new stuff from the downpipe back (cat, muffler, tailpipe). I am looking to find a head/intake and port/polish and match it. When that gets done (probably this fall), I will go with the borla and some re-wiring of the sensors. I cant believe how much they really changed. My '95 and my '01 are so different! Crazy to swap the head on an engine with only 45000 miles on it? Well, it was a salvage title, so no warranty anyway! Maybe I am crazy, maybe I should supercharge while I am at it. Anybody got a spare powerdyne lying around? I am going to go broke.
-Jon