Although the tires on the rear needed replacement, they did not fix I guess what you would call the issue, if it should even be considered that.
While driving home from the tire shop yesterday, I noticed a bit of resonance even at lower speeds of 35-40 mph in 3rd, which is about 1900-2000 rpm. Again, mainly feeling it under my seat, or towards front portion of drivetrain, but the sensation may just be traveling up from the rear thru driveline.
When popping the trans in neutral on the highway, the resonance is still there, but a bit less magnified. There is some roughness, as mentioned, when revving in neutral above 2000 rpm thats been present since the new motor mounts went in.
Thought about wheel bearing or axle bearing recently. Going to put the car up and check for wheel wobble, re check the ujoints, ect.