I found that if I moved the X carriage back and forth along the gantry, I could feel a very slight wobble. But, the hot end was not loose. I was not a wobble, but more like a waving. It seemed that one or more of the new wheels that I installed were out of round. But, which one(s)? And how could I determine this?
I replace the new wheel with one of my old ones and the symptom greatly diminished. I am now waiting on my third set of highly rated wheels from Amazon (from a third source), as the two first sets from two different sources had many bad wheels. Do you have a source for high quality wheels? Please let me know in the comments, as I may not yet have found one. But, I will post an update when I do.