Originally Posted by 5_Liter_Eater
It is normal for a stock tune to have a mountainous looking PE. Why they do this I don't know. As you know, tuning AFR on the dyno by playing with the PE further in order to achieve a particular AFR throughout the RPM range is an old school, dare I say hack, way of tuning AFR.
You're doing it right by flatlining the AFR and calibrating the MAF table(s) until the desired AFR is reached throughout the range. After that the only step you could take would be to slap it on the dyno, make a pull with the PE at, say, 13:1 and another at, say, 12.5:1. Match up the dynos and see where you gained and lost power. At the RPM points where you gained power, keep the 12.5 AFR, where you lost or stayed the same go to 13.5:1 and make another pull. Where you lost power (in relation to 13.1) go back to 13:1, where you gained, leave it at 13.5:1. Now your Pe is mountainous again but the numbers are accurate. You know you're getting the AFR you're commanding and that the AFR's you're commanding at each RPM make the most power.
Disclaimer: These AFR's are just examples for NA gas vehicles.