Every car maker does this to their mass production vehicles. They tune it to run rich in the higher rpms, to cool combustion off and lose power so you don't feel like revving out that high. It's for longevity and safety. On my car it starts richening from 13'ish afr down to 12.5 around 7600 rpms, then by 8000 it's 12.2 and at the rev limiter of 8200 it's 11.9I have unhooked, and packed away my scanner, but I will upload a phone pic of the dyno sheet tonight.
My dyno guy also runs a wide band O2 sensor in the tailpipe.and I notice my power falling off as my o2 goes from 14.7 to around 12.0. Is this typical?