The tires should be inflated to the tire manufacturers recommendations.
They rate the pressures based on your actual weight so you'll need to visit a truck scale loaded how you normally would be while traveling. If you have the Michelin XRVs 90psi is too much and really more than the chassis can handle anyway for weights.
Michelin Tire inflation guide is online here
Make sure you click the right wheel size and find your tire in the chart. I'm sure Goodyear has something similar.
They really want a 4 corner weigh so you can see how much is on each tire and use the maximum, but I haven't found a scale that will do that yet.
I've attached one of my scale receipts from when we did a heavily packed 10day trip. As you can see, I was pretty heavy. I was within 380lbs of my GCWR since my car is so heavy, YIKES! An empty 357QS is 680lbs heavier than my 350TS, and a 378TS is 460lbs heavier so your weights may be similar if you're half the pack rat I am.
I had 6780lbs on my front axle which is 3390lbs/tire. The chart says I could run them at 70psi but since I don't know the exact tire weight I run 75-80 and maintain some safety margin.
I had 14280lbs on my rear axle which is 7140lbs/dual. Chart says to run them between 80-85. I run them at 85.
My toad is the last weight on the receipt.
I had many complaints about the ride and handling of my chassis before getting the tire pressures correct. It's better enough now I have little thoughts about any other chassis upgrades. Running the right pressures insures will get you the most life out of your tires and give you the best ride.