Lexus Forum - Lexus Enthusiast Forums - SC400 Vibration and Hum..What the heak!

Need help with my SC400.https://lexusforum.com/micons/m14.gif Has a vibration in the front of the vehicle. Slowly has gotten worse. Thought it was torque converter area and forward. Replaced flex plate, torque converter and transmission. This did not solve the problem. When I am going down the interstate there is a pulsing hum while my foot is on the gas. When I let off of the gas, the hum stops?! Getting louder and louder. Has developed a slight vibration! Have been told it could be the motor mounts. When the car is sitting still, inneutral, you can give it gas and there is no vibration or noise. When you put it in gear, it immediatly starts in. Not made of cash here...could really use some practical solutions or ideas. Love my car, but somethings gotta give!
Thanks!
Lisa