This is correct, the CA Emissions have 4 sensors, the CA-Exempt Emissions have 2 sensors. See diagrams below for sensor layouts...

CA Emissions:


CA-Exempt Emissions:


It shouldn't be that hard just after driving it, like Old_School said use some PB Blaster and let it soak then try and use a crescent wrench or vice grips to break it and then let the exhaust cool down and twist it out the rest of the way. If you have a CA-Exempt Emissions exhaust layout just look at the CAT and about 6 inches before the inlet you will see the O2 sensor.

 

What is PB blaster?

 

penetrating oil, it helps break down rust.

 

If it were the O2 sensor would it not throw a code? Would this explain the worse than normal gas mileage?

 

02 senors won't always throw codes, in fact more often then not you will get codes for something else on top of poor fuel economy.

 

yes O2 sensors would explain poorer than normal gas mileage, and no they dont usually throw a CEL code.

 

A bad O2 sensor will almost never throw a code unless the downstream O2 sensor notices a change in performance from the catalytic converter, or there is an electrical issue with either one of the sensors or wiring harness.

Typically more times than not an O2 sensor code, even if it's thrown, for running too rich/lean will be a faulty sensor.

 

I ordered the O2 Sensor. The shipping cost as much as the parts. Canada really sucks for auto parts.

 

Okay I installed the OS sensor a couple of weeks ago it actually wasn't that bad to get the old one off. I only drove the truck twice since then but the problem seems to be gone. When I changed the sensor I observed that the cable clip was broken off so it could have been a bad contact as well. I have one more question. Are there gaskets that go from the manifold to the Y pipe? I have changed the mounting flages because they rusted out but it is noisy now. Please let me know and thanks for your help.

 

Are there gaskets that go from the manifold to the Y pipe? I have changed the mounting flages because they rusted out but it is noisy now. Please let me know and thanks for your help.