I'd realized that my car is running too rich, and gas mileage just isn't what I thought it should have been. I did the research and bought a Bosch 15725 at a local parts store. I was a little concerned about the Cali emissions and the non-Porsche o2, but it worked fine. The little gizmo that Bosch includes to splice the sensor into the stock harness worked with no issues.

The old sensor must have been totally worn out. I started the car, and immediately noticed the difference. The car is waaaayyy smoother, and I don't have that flat spot in the RPM until the car warms up. We'll see about gas mileage, but I can't imagine that it would not get better.

Now I've just got to nail down the Gas fumes in the passenger compartment after a fill up.

 

Bump for a useful thread.