I believe power checks are best done into wind, to maximise cooling, and this was critical on engines like the merlin. Unfortunately some pilots think you can only do power checks into wind, so if your doing power checks, a little consideration for other aircraft that are likely taxi behind you is good and incline the aircraft forty five degrees either side of the wind. I can't really see that there would ever be a need to do power checks with the wind behind you, unless it's a very light wind.