I have always noticed a "rumble or shake" around 80mph, I wasn't throwing codes so I figgured it could be the drive shaft or tires or something. I reciently started throwing the 430 code for the cats and decided to try these O2 sims from ebay.... I put them on and now there is no "rumble or shake" at speed and I can really notice a gain of peppyness through the gears. I'm sure I was running off the air/fuel mix even before I was getting the 430 codes.

http://cgi.ebay.com/ebaymotors/ws/eB...6fvi%3D1&item=

 

O2 sims after the cat have no effect on engine operation.

 

The rear 02s have nothing to do with engine management. Frankly, those just look like more ebay gimmicks that are nothing but a drain on the wallet.

 

yea, sorry bud, but its prolly all in your head...i know after i put my skip shift in, it felt sooo much faster, and while it didn't take as long to row through the gears when daily driving, it didn't make sense in my head that id be faster with just this tranny anti-lockout and i thus had to convince myself that i didn't gain any hp yadda yadda yadda. take the sims out, unless you are gettin an ORY anytime soon, and sell them to the next poor soul on ebay

 

Just an update on this if anyone wants to know. Also thanks for the advice as I just got the car back from the dealer and they replaced the cat for free under manufacturer warrenty. The bad part is that now I remember why I was trying to avoid the dealership, They want to do $700 dollars of other work while they got you trapped there, I had no part of it. They wanted 60 for a fuel filter, 140 for injector flush, 140 for a O2 sensor and 358 for a window motor which is a little slow but far from needing replaced. An O2 sensor at the auto store is about 70 so I will get that because I am now throwing P0135 codes. Anyway let me know if you blame me for trying to avoid the car dealerships, that is probably why I tried the other gimmick part, but I still believe the car ran better with that in , but only at high speed 80 + mph.

 

Why pay a parts store $70 for an O2 sensor? You can get an OEM AC/Delco O2 sensor for about 1/2 of that using the GM discount parts dealers that are recommended here often. Courtesy of Shoebox:

http://shbox.com/1/4th_gen_tech2.html#Dal_and_Jason

 

UPDATE #2

So I got my cat replaced and needed to replace the O2 sensor , I did get a deal on 2 new sensors (70 for both) one pre cat and one post cat. I figure how hard can this be, so I raise the car up and try to remove the sensors and "what the F" they wont turn, even with the exhaust hot ! So I give up and take it to my local shop where I know the guys and I'll be da*ned to find out when the Chevy dealer put the O2 sensors back in they stripped the H*ll out of them so bad They had to be heated up and use an air wrench to get them out. Then we had to weld a nut in the hole to be able to get the O2 sensors back in. Thanks Classic Chevrolet on 434 you guys suck!

 

sounds like a good reason to get long-tube headers to me!

 

Seeing that you had the 02 sims, I'm surprised you just didn't gut the cats if they were bad.

 

Yea, u usually need a tourch, or a foot long breaker bar