no problem. like i said the ebp valve should open completely if unplugged, no whooshing out the exhaust.
now, if your going down the road and you hear this valve opening and closing (still plugged in), that is normal, it will do this until the engine is warm. BUT, if you punch the throttle, it should open up completely (youll definetly hear it), and close a couple seconds after you let off.

what im trying to say is, if your going down the road and you punch it (if it doesnt open right away let off, only takes 42psi of backpressure to lift an exhaust valve into a piston ) it should open, if it stays completely closed to the point where it pretty much wont go, your ebp sensor is probably bad

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and reading again from your first post, you said that you replaced the ebp sensor?

how long have you owned the truck, from what you actually described, the ebp valve seems to be functioning properly. the valve will only start working if it's 35 degrees or so outside. parking it in your garage (im assuming its a little warmer in there) would explain why it wont do this afterwards. but unplug it, see if you like it better