I'm just giving you a hard time. . .last year I was trying to read the ingredients or instructions or something on a box and without even thinking about it, and for the first time in my life, I had to lift up my glasses and squint in order to read it. When I realized what had just happened I gasped (with what was no doubt one of few remaining breaths).One day all you whippersnappers will need the larger print too.
Took the CT into the dealer and they said rotors were warped.I have an adjunct question - you say it only happens with light pressure at about 70mph, right? What happens if you were to give it heavier brake pressure at that speed, does it go away?
Have you brought it to your dealer to look at this yet? First things that come to mind are: loose/bad fitting brake pads (or shims that help hold them in), or rotors that need to be re-surfaced
Sometimes the symptom you described can be explained by: not vibrating at low speeds due to rotor not spinning fast enough to incur this specific vibration; vibration goes away with heavy brake pedal because it's clamping down so hard that the pads & shims have no room to vibrate, and the rotor is being squeezed hard enough on both sides that it can't vibrate any more.
Not saying that's it for sure, but, if those are the symptoms you're seeing, there's a fair to midland chance. . .