Need your experience

Thanks for all the replies! Greatly appreciated. Just had a call from the garage (9:20 pm) on a holiday weekend. Somewhat impressed by that, I must say. They said it is probably a vacuum leak as was suggested. The vibration happens at 45 mph and goes away so they are not sure but thinking drive train issue. Only happens at 45. They were very apologetic and promised to make it right. I wish that we had thought of hooking up the ODII but wasn't even thinking of that. We went ahead and came home this afternoon so we are not there to do it now. All about timing sometimes. Thanks for the encouragement as well. On days like this, that's what we all need.