This is a topic I have a vested interested as I work with engine dynos in my job. Just to give you some info in each test cell ( similar to stus) we have a fully independent weather station. This measures temperature pressure and humidity values. This information is fed into the automation system so we can have engine power corrected to the the sae standard.
We can also tweak these but we aren't chasing numbers like some chassis dyno operators (and their customers) are