The reason you see the correct values when you are crusing is because you are in closed loop where the O2 sensor is feeding bcak to the PCM and then based upon the O2 readings the PCM injects a certian ammount of fuel. The rich code that you are getting is because in the PCM software there is monitor that looks at the pulse-widths of the injectors. There is a base map of these pulse-withs built into the PCM and then the PCM adjusts these values based upon operating conditions that call for more or less fuel. This adjustment is of course limited to a certian ammount each way (rich and lean). This is called adaptive memory. There is a long term and short term fuel trim. So say you reset the PCM the base values are used for fuel injection. Then when you drive the PCM sees that at x RPM and x pressure (or whatever values the pcm uses to base the adjustments on) there needs to be either more or less fuel injected. So then the PCM remembers this and stores the adjustment values in the RAM of the PCM. So the next time your engine is at the same condition the correct ammount of fuel will be injected. So what is happening to you is that you are injecting too much fuel according to the PCM and then it adjustes it lean until it cannot adjust anymore and then it sets a code.

So i really think that the stock ECM is quite awesome that is why i prefer using stock fuel injectors and then adding some secodaries for boost this way you get to keep all of the neat features of the PCM and get good reliability and driveability.

Heres another way of explaning it according to one of my books:

Adaptive memory allows the computer to adjust its memory for computing open-loop operation. Once the system is operating in closed loop, the computer compares its open-loop calculated air-fuel ratios against the average limit cycle values in closed loop. If there is a substantial difference, the computer updates, its data and corrects its memory.


So how do you find out what your fuel trims are? Use your laptop and get a scan tool that you can hook it up to your laptop and datalog your fuel trim values and then you can see if you need to richen or lean up a certian point. Now don't worry about these values in boost.

Mabye you are wondering why there is a long and short term fuel trim now well here goes. The short term i used for quick corrections such as a change in barometric pressure, hudimity ect, since all of those factors affect the engince volumemetric efficiency. The long term job is to monitor the short term values. If the short term is always at a high or low values it will then compensate in the long term and set the short trim back to its original/zero setting.

So this i just a breif overview of some things and it may not be 100 percent correct so anyone feel free to correct me as i am writing this and watching family guy so my attention to detail is limited.
Hope this helps and enjoy the wideband (i also have a zeitronix and i love it)