Lack of thrust when below 120 knots.

[Lee Dove]

When flying the Corsair if I let the speed drop blow approx. 120 knots I can never recover it. I can fly happily at 200+ all day, gain speed lose speed no problem. However once the speed drops below 120 even with full power and prop speed 2600+ it is as if I have massive drag or the prop is not generating thrust. Anyone else seen this? It is very consistent for me.