[Beaner81]

I have a 98 Chev K1500 with the 350 vortec and I have been getting horrible mileage for the past few months. I have been asking around and never getting the same answer twice. Finally the other day my service engine light came on so i took my truck in to autozone and they plugged it in and got a bad oxygen sensor bank 1 sensor 2. They told me to replace the one after the cat so i did and my light came back on the same night. I have more than one oxygen sensor and i now understand how they work and why i have been getting bad mileage but i cant seem to find anyone who knows which sensor is bad. I hate guessing at 65 bucks a crack. Can someone please shed some light on which sensor is which or if i replaced the correct one then why I am still getting the same error code in my computer?