Ended up returning the Michelin Primacy MXM4 tires. Went back to new Michelin Pilot HX MXM4 tires.
The Pilots are much quieter than the Primacy to the tune of about 3 to 4 DB at 70 MPH on the same road according to my decibel measurements. But the real benefit is eliminating the awful and irritating hum between 40 MPH and 80 MPH. I Googled and found a few reports of the 70 MPH hum with the Primacy tires. So I am not the only one to hear it. After about 400 miles the Primacy tires did tend to get quieter, but not to the level of the Pilots new.
I am amazed how different the cars drives with each set of tires. The Pilot HX MXM4's are much more stable and have less drift when going straight. The car feels planted to the road and has a little stiffer ride. The Primacy tires give the LS a much lighter feel, sort of a floating feel and easier turns of the wheel. Not a bad feel, but much different. Both are the same in terms of grippyness.