Trouble tracking down a noise....need help please

I am get a rumbling when I am driving at 50 or above. The minute I let go of the gas or turn a little to the left I get a non stop rumble. A light
tapping noise. I can feel it at the floor board. Any ideas? It goes away if I step on the gas or the brake. I don't think it is the brake because it only does it at high speeds. Any ideas? Thanks
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.