Well sadly, he is an idiot.
Dyno variance in most cases is +/- 15rwkw, thats a reasonable range.
80rwkw, thats just plain horse shit
Put it on the dyno - and not for a rwkw figure.
Use it to see the AFR's, the power/torque/boost graph and so on. Will tell you exactly how the car is performing and is a MUST for anyone modifying