Im Installing a set of pacesetter headers and Y pipe, and i took off 4 O2 sensors but i can only put 2 back on, Which sensors do i use and which harnesses do i use to plug them back in

 

You'll need o2 extensions for the headers, but all 4 o2 sensors are identical in function. Not positive, but I believe the front/back might have different wire lengths.

 

i got the extentions. so does it matter which harness it goes to? i would assume that because some people use the extentions i would plug them into the back harness, but if they both function the same then it shouldnt matter, right?

 

Hello , yes it matters , the front 2 closest to the engine are the ones the computer uses to help decide the short term and the long term fuel trims . The 2 furthest from the engine tell the computer if the catalytic convertors are doing their job , I'll assume You're not worried about passing emissions with this vehicle . The front 2 are the ones just using two . Good luck

 

You will need to use the front 2 O2 sensors as they are the ones the computer uses to decide how much fuel to give the motor. The rear 2 O2 sensors are used only to verify that the stock catalytic converters are working correctly. I would make sure you either extend the stock wiring harness or grab some plug and play extensions.

 

How can you visually identify the front sensor, is it longer then the rear. I mixed mine up when taking everything apart, stupid I know. So I just swapped mine around until I got the SES light to stop coming on, all done within 10 miles of slow driving.

 

Actually I tried of searching for the original O2 sensors acdelco ones ( AFS-98 & AFS-97 ) but I went with Walker brand and they do the work getting me 14.7:1 all the way ..

Actually you need extension for the front sensors

Don't get confused the harness for the rear ones after longtubes will be near by the front O2s in you LTs .. the one you need to install the extension is where around the K-Member