Alrighty... So, I have an FSwerks race header on my Zetec.
Everything was going awesome for a long time. Like, since March. So I know it wasn't "biased" because of the header.
I made my own O2 cheater using the resistor/capacitor trick, it's still doing awesome for the downstream.
Now, I'm getting a P02195 (Upstream O2 sensor biased/stuck lean)
and I'm thinking since it's obviously the original one that came with the car, and it's 130xxx miles old, it's just time to change the sensor. I already ordered an NTK p/n 22060 from RockAuto.com.
Is this a good assumption?