Hi, my 2006 GMC Envoy XL (4.2 L) with 154k slightly vibrates when I come to a stop, but when I put the transmission in N or P the vibration completely goes away.  The car shifts up and down just fine.  Sometimes, when I drive when the car is warm, like after pumping gas, for the first 5 seconds, the transmission feels hesitant and you can hear a loud whooshing noise (like the transmission is cavitating) but the sound appears to come from under the hood. I have replaced the air filter, spark plugs, spark plug wires, replaced auto transmission fluid (level is fine), and flushed the radiator, motor mount and transmission mounts are in good shape. Also cleaned the throttle body. Still does the same thing!  Thank you in advance for any advice.