catalytic converters

[trego]

Need a little help.

Car in shop. Diagnosis from independent is "clogged converters"??!!

Problem is runs rough on start and under load if you give it any gas at all it stumbles.

ran rough for one to two minutes for approx. three months but drove fine as soon as engine came up to temp. new stumble problem showed up two days after i put new pathfinder exhaust from rear most "cat" all the way back. ( Had to relocate one hanger) yes I did put ground strap back. What is that for??

co never gets rich no matter how much pedal you use.For and aft co2 give same readings. no differential.Only code is lean left bank. he cleaned mafhe wants to remove both converters and road test.of course he is not going to be responsible when he breaks off all of the bolts.

Question:

How many converters are there? Two or four? What are the two smaller units between the converter and the intermediate pipes?

Are Eastern replacements O.K.?Catco seems better because they come with heat shield and gasket.

Any reccommendations on vendors or other after market manufacturers?

Is this a viable diagnostic path?

Any help, comments, guidance and/or hand holding would be greatly appreciated

[trego]

After some thought and reviewing many posts on this forum I told the shop to stop working on my car put it all back together.

Installed a new mass air flow sensor today and that was all it was. Just coincidence that the new problem showed up two days after replacing the exhaust I guess.

I am very thankful for this forum.

Still interested to know what the ground strap between the exhaust pie and the body is for and what the two smallish units downstream from the catalytic converters are.