BHP measured at the engine, no. WHP measured steady-state, no. WHP measured while accelerating, yes, because you will have less power losses from spinning up the rotational mass of the wheels. Lightweight flywheels work on the same principle.
http://www.uucmotorwerks.com/flywhee...heel_works.htm
Whether this power gain will show on a dyno depends on the type of dyno and how it measures HP. An inertial dyno would theoretically see a difference but I'm not sure if it's large enough of a difference to show up.
https://en.wikipedia.org/wiki/Dynamo...of_sweep_tests