Another thing to try (if you happen to have free time at the dyno) is to disconnect just the Yaw sensor and see what the car does. If it goes past the 4800 RPM mark, then it disables the ESP and allows a full RPM run. We have all have our solution. If not... nothing lost.

The only reason I had a full pull was because I was on a AWD (all whee drive) dyno that had the rollers linked. I also got kinda low numbers and I think it's because of the extra rotating mass.

Cheers!