[jhv48]

Tom, here's another thought. The Nitto 555 G2's are harder ( treadwear 320 as opposed to 240) than your previous F1's. Try lowering the tire pressure to around 18 lbs. and see if that helps. I always try to stay with tires that have a 200 treadwear (soft) and keep my pressures down to 21-22 lbs.
Also, are you sure it's the fronts vibrating and not the rears?
I went through everything you've done. I replaced the wheels, tires, ball joints, tightened up the steering, replaced the shocks, and balanced and aligned the front end many times.
I finally found a pro who had the hunter road force GSP 9700 balancing machine. He spent some time and after rotating the tire to match the wheel, my problems were solved. If your guy isn't using that machine, find one that does.
It's the tires/balance. Our cars are so light, they need the wheel and tire to be a perfect match.