Wierd vibration...

[sirroada]

So here is the story...
Bought a new S-works Tarmac off the shelf on clearance. It was a leftover 2015 that no one had purchased. Absolutely sweet ride, smooth, fast, matte black/white color, duraace, Roval Rapide 40 wheels...all the goodies. But after two weeks of pounding the pavement the matte finish started peeling on the rear chainstays. So, I took the bike back to my LBS and asked if there was any way to fix it. They took some pictures, called Specialized and the verdict was...we don't fix them, we replace them. So kudos to Specialized, they sent me a brand new 2017 S-works Tarmac frame. The LBS swapped all the parts from one bike to the the other.
Got the new ride back...its sweet BUT...The new bike has an annoying vibration that starts around 20mph and gets more noticable the faster you go. Its enough to make my hands go numb. It is definitely speed related as I don't notice it at any speeds under 20, it is always present, never intermittant and it happens whether I'm coasting or pedaling. It is NOT frame wobble, it is a vibration. It seems to lessen if I unload the rear wheel by leaning my weight forward onto the handlebars.
All the parts are tight on the bike. I did notice that when I hand pedal the bike in the bike stand there is a lot of up and down movement of the rear wheel, almost like its out of round...but it isn't. I pulled the tire and tube off the rear wheel put it back on the bike, spun it up and it still had that bounce in the bike stand. Could that be it? Otherwise...what are your thoughts?