You are right, the Z has 2 sensors on each side, one before and one after each cat. On 03 and 04 all 4 sensors are 02 sensors on the 04.5 and up the sensor before the cat was changed to an AF sensor, basically a wideband, and the rears stayed 02 sensors.

 

Thanks guys for all the input and help.

As for an air leak, I doubt it. The car idles perfectly smooth with no rough spots. I was extremely careful doing my gasket install and never got near the injector harness, cables, or clips. The area you work on gasket just doesn't get you that close to that.

It could be the sensor. If they are not expensive I might pick one up and change it out myself. I would rather invest a couple $$ on a small item than deal with a dealer situation. I would propably run into issues of them pointing to all the mods since they are breathing related and this just happens to be a breathing related problem.

They may point at the intake, the spacer the hiflo cats, who knows they may even try to invalidate my warranty with that premise. I know that legally they shouldn't but we know that they can make you go thru a lot of headache in the meantime.

 

I reset the code tonite and observed something interesting. For the last 2 times I reset the code I didn't drive the car until next morning. Well morning in Miami is warm this time of year. The code would come right back within 20 minutes of my morning commute. Always by the book. Engine warm and holding rpm at around 2K.

Tonite I reset the code for the heck of it and went out on an errand. I expected the code to pop up as usual but not this time. I ran at 2K for a while trying to cause the code to pop up but no way. The only difference is the temperature. It is a bit cooler than in the mornings.

Anyone have any further input given this observation. Does the temperature difference have any indication on the possible cause. I was hoping this would point more directly on the possible causes of AF sensor, fuel pressure, fuel injector, or intake air leak.