Stock 2001 gs 430 155k miles

I have had a check engline light for quite some time. I got the codes read by 2 diff mechanics and both told me "the cats need replacing" Neither were very friendly, and they did not give me the specific codes.

Car drove fine, so I just ran it. FF 1 year or so, and my y pipe rusted through with holes, and I ordered a new one from eastern, including the rear cat. Long story short, I couldnt get one of the old o2 sensors off the rusted up pipe, and I installed it with a plug in bank 2 sensor 2 hole. ran great for 2 months, then started running like ****. Sputtering. bad mpg. no pickup when at low RPM (smelled like gas when you mash it)

Since the time i had my codes read, I did ALLOT of research on here, and I see that ussually the 02 sensors are bad (not the cats).

Currently my car is on blocks, and I have the Y pipe/rear cat off, and before I put it back together with both the old sensors (i finissed the stuck one off the rusted y pipe)...im wondering the following :

Are there any codes that would have told these two "mechanics" that specifically my cats were bad, or were they mistaken, and most likely my sensors were bad ? I really dont want to put it back together, just to bring it in again to get the actual codes, only to have to pull it apart to put in new sensors. Also dont want to put new sensors in only to find out that my front cats really are bad then have to pull it apart again. Not to mention im from North NJ and its fuggin cold.

Thanks

 

Cat code consists of checking for exhaust leak, post oxygen sensor bad and last is the cat itself

 

thanks

post sensor = the downstream sensors ?

any idea if running without the bank 2 downstream sensor would make my care run like crap ?

 

Yea downstream

 

thanks. I'll try those first and see what happens.