pinion angle opinions wanted

My car has a slight howl and vibration to it when light on gas. I just had driveshaft re-balanced because of it,and that did not change too much. So I think it is pinion angle related,I took all measurements off of u-joint caps and this is what they are. Trans tail shaft is 2.3 degrees down,front of driveshaft is 3.7 degrees down,driveshaft at rear axle is 3.7 degrees down. and rear axle is .5 up. The tool that I am using shows a working angle of 2.3 degrees on rear u-joint (if I did it right). Looking for any opinions if this could be my issue or not. Thanks