Yeah, a lot of people repeat the mantra that "Bosch is no good." But I've never seen a post where they actually tested the sensor in any useful way. I use a generic sensor, it works great, and I have actually looked at the signal on a digital oscilloscope. So if someone actually runs a comparison on O2 Sensors I'll be eager to look at it, but otherwise it's just so much talk.

By the way, two O2 Sensors (up and downstream) means it's a California truck. Almost all years. When the upstream sensor goes bad (or, more likely, the Catalytic Converter goes bad), the downstream one detects it and throws a code. No code means the upstream sensor is still working. It might not hurt to replace it (I did), but don't expect miracles.