Quote Originally Posted by Drop Top Olds View Post
...four wire O2 sensor....
For city driven vehicles, this is a good upgrade, three or four wire O2. I drive country/Hwy miles mostly, so its not an issue since extra heat is passing by O2.

In forum topics, I've heard of cold O2s causing issues during vehicle smog inspections. I assume its carbon (i.e. oil) deposits fouling O2 sensor. A rich condition would be expected when fouled, by electronics design.