Yeah, that's most likely a protection routine. When you don't have a lot of airflow through the car such as when it's on the dyno it will pull power to protect the motor. It does this by doing several different things such as running richer and so on. It looks like that's what's happening.
Your quarter mile may be slower if you're spinning tires at the track... was your trap speed higher?
If you have a vag-com, we can run data logs on the road to see if everything is running correctly once you have proper airflow over the car.