Just a thought, wanting to make sure I'm thinking straight. If the opti is causing a misfire in any/all cylinders, this could in turn cause a rich condition due to unburned fuel, correct?

 

yes but it will also cause you to read lean at the same time, big spikes of rich/lean.

 

What it actually does....

When there is a misfire, the unburned "air" (= 22% oxygen) goes out the exhaust, and is "seen" by the O2 sensor. The sensor reports "lean" to the PCM, and the PCM increases fuel to all cylinders on that bank with the misfire. They all run rich, becaue the PCM thought they were lean.... but it was a "false" lean.

And remember, the O2 sensors can not measure "fuel", they can only measure "oxygen", so a blast of excess fuel isn't going to do anything. Its the unused air that causes the problem.

 

Ok, thanks. I was wondering because I believe my opti is the blame for my miss and hesitation and breaking up over 6000 rpm, and the car was running rich to boot. Looks like I'm on the right track in replacing the opti. thanks guys!