Hate to be so blunt, but if you want a bike that's stable at high speeds, you bought the wrong one.
I struggled with the high speed wobble issue for 4 seasons. I tried everything, including
-new head bearings, at various tensions
-fresh tires, at various pressures
-Progressive springs, 1" lowering blocks
-sliding forks up/down trees
-various settings on rear shocks
-Removing flyscreen/sissy bar
-fork brace
-frame braces
Some things made an improvement but it was never stable much past 90 or so. It was possible to make top end runs to 140+, given perfectly smooth/straight roads, the riding posture, and it was the second Tuesday in the month, it wouldn't shake, but you could tell it was always right on the edge of doing so. Leaning it over much past 85-90 usually ended up with a nervous, shaky feeling that encouraged you to back off.
Here's my tips/best setup....
Metzeler ME880 tires, 110 front 170 rear. 32psi front 36psi rear (I found over-inflating to have no noticeable effect, though underinflated tires most definitely made it worse)
Progressive fork springs, zero air psi, 1" internal lowering
Head bearings set "3 good taps" past what the bounce check suggests. The bars would not fall to the stop on their own. A bit tighter and a low speed weave emerged. This was a lot of trial-and-error and I found this to be the best.
Forks slid up trees 3/4"
Rear shocks set at minimum preload and maximum damping. I weigh around 180-185 in gear. Again, more trial and error.
Feet on highway pegs at speed. For whatever reason, this instantly made the bike more stable than if they were on the regular control pegs.
Keep a loose grip on handlebars (i.e relax the death grip, pulling back on bars makes wobble worse)
Don't shift gears past 100 (if exceeding 100, run up in fifth, don't wind out 4th before shifting)
In the end, I ended up selling my Max because I couldn't fix this problem. Drove me absolutely nuts. Finally realized that this bike just wasn't made for high speed operation. It was designed to blast between stoplights. Intended for acceleration, the high top speed was kind of a side effect Yamaha didn't seem to pay a whole lot of attention to.