Engine Mounts

I am getting some weird throbbing vibratioins when I am going about 45+ mph. I also notice that when I get that vibration and I turn to the right in a somewhat tight turn, the vibrations goes away. I think that the g-forces shifts the weight of the engine off one mount onto another during the turn. Also this noise seems to only occur when I am in 5th gear. Any ideas?

change your engine mounts.