I'm pretty sure its (engine mount change) going to make a significant difference then what you are currently experiencing. The deal is many of us are meticulous on expectations of refinement that we expect in the BMW product. I knew something was wrong in my X5 with regards to the vibration because every time I got into my E39 M5 or my E39 540i wagon those kind of vibrations were not present, didn't feela thing in the steering wheel. My M5 has 92K miles and 540I Sport wagon had 173K miles, granted I changed the engine mounts on both of those vehicles, M5 at 91K and 540i wagon at 165K. So to get into the X5 and feel these slight vibrations in the wheel was just killing me. I did not really want to change the engine mounts at this juncture because its a lot more involved than the E39 cars but I had to take the plunge to get to satisfaction. By the way on the X5 I changed all of the tensioners, the alternator and power steering pump were new when I got it. So I eliminated most other areas where the vibration could be coming from and finally came back to the engine mounts.