you made a WOT pass with a buddy holding your engine cover open that doesn't sound very safe. If you picked up any rpm I would imagine it would be from cooler air not more of it. a 3" hole can flow more than enough air for you engine. With the hatch closed the heat from the engine heats up the air under the hatch making it less dense which means less power:frown:
so the answer to your question is no your engine is not starving for air.
Omega