weird sound

Hey Guys!
I have this sound coming from my vehicle. It kinda sounds like a bicycle having a hard time getting into a gear. It is not that exact sound but close. It sounds like it is coming from the front of the car. It happens if I have the car weighted down and am driviig up a mountain road or if I am passing someone at highspeeds and am flooring it. It does not make the sound at idle or if I rev it up to like 5k. My acceleration is smooth and my car shifts great, it is a 5spd manual. Everything is stock the only thing I have done to it is remove the air silence 3 years ago.

Thanks

Jody

Any other ideas. I am still not quite sure why you would say suspension though? It almost sounds like I have a bunch of leaves in my intake, but that is only when i hit hi speeds, bot not when I rev it in a stationary position.