For me, my 07 XLS seems to run best at 35 psi.
I have the H rated Goodyear tires.

 

If you want extreme handling, and loooong tyre wear (like 88000Kms) but be buggered with a soft ride - put 38PSI in each tyre. I did this religously when I had the original rubber, and yes, I got 88000Km out of them. I now have offroad boots, so only put a max of 35 in 'em. (the max is 38 as per sidewall rating) Of course, only ever check tyre pressures when they are hot. zgo for a 15 min drive, do a little hard cornering & braking to ensure you have a good build up of heat, then check them quickly - you would be surprised at how quickly the temp drops off. So far I have managed over 75000K out of two sets of offroad rubber, and am on my third set now. Even with these taller tyres fitted, I can out-corner a lot of mates in sedans, albeit with a lot of noise and front end drift. Once you get used to it, the understeer is great - just modulate the accellerator for controlled drift & steering input! Not the best for good tyre wear, so use it at your own discretion!

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Manual says measure it when they're cool, inflate to 33PSI. i bet starting from there it'll get to 35psi easily after a short drive

 

Agreed, you should always measure the tire pressure cold. You can easily gain 3-5 psiwhen driving from friction/heat build up. If you use this logic you should never exceed the max psi listed on the tire and won't go too low when the tires cool.

Also you might have uneven heating on one tire making the pressure you add less or greater than the others giving uneven wear and possible steering/drifting issues.

Coolmael,
What the road noise like with your offroad rubber?

 

The Yokohama Geolanders G033's on my 08 ES are at 38psi on all fours. This is what the dealer put them at during new car prep, and when I questioned the service advisor about it, he said running at 38psi will give better mpg and better wear on tires. He also said the only reason mitsu recommends 32psi is for a smoother ride. The max pressure on these tires is 44psi. At first I wasn't sure since I've never had a vehicle that ran the tires that high, but now that I have 1,000 miles on it, its fine, and if it gives better wear on the tires and a little more mpg thats great.