Hmmm...I know other people have mentioned a "dead spot" in a certain rpm range. The new Vmax throttle body is supposed to take care of that. Not sure if it would help with the vibration issue.
I can't really say that I've noticed any weird vibrations at 45 mph. My rear view mirror will shake a little during a cold start, but after that it's smooth. I also usually run 93 gas, so not sure if that helps, too.