It's a MAHA and we see anywhere from 70-120 on these platform cars depending on wheel/tyre combo, strap tension, tire pressure, etc but the calculated bhp is always the same regardless of the difference in whp and bhp.
We calibrate for vwr cup race teams and they have to certify their power at other dynos and even though the other dyno reads whp higher and losses less, the bhp is always the same as ours.
I would say the explanation for such results at stage 1+ is that turbo cars love the cold weather.