It is the shape of the sidewalls that should give you the clear view of what pressure is needed based on the loaded weight of the vehicle.

Here is what Cooper Tyres (or is it Cooper Tires?) say: Tyre Pressure Guide - Cooper Tires Australia | Tyres Worth Owning

 

That link made for an interesting read whilst on the dunny bucket this Christmas morning.

Plenty of room for the turkey and pud now too!

Cheers!!

 

I'd be running around 40psi and keeping an eye on the tread wear.
Look at the max pressure on the sidewall for an indication of what the tyre likes.

 

The Touareg uses much lower pressure than the Cayenne does. I've upped my pressures to 40psi front/rear and the handling is significantly increased.

 

Im actually running that exact tire on my 13 TDI sport. im not a tire or suspension designer i believe the rear pressure being higher is meant to handle full gross weight or maximum trailer weight. in other words its too high of a pressure for daily driving and groceries.
30 psi front and 34 rear felt nice to me. quite a bit smoother but still plenty of sidewall firmness to not feel squirly on freeway ramps.(im used to messing with tire pressures for track days and autocross) but the low tire pressure alerts have been driving me crazy.

 

It's a 5000lb SUV that was designed by one of the top sports car manufacturers in the world. The front to rear pressures are offset to induce understeer. Also, in my opinion, they are lower than the cayenne to induce a feeling of lower handling capability vs the cayenne.

If you look at the cayenne factory pressures they're significantly higher AND they're barely offset.

Lower tire pressure are going to lead to sloppy handling, lowered mpg and more aggressive tire wear.

 

I totally agree, the Porsche sibling is gonna handle the tarmac way better. And naturally each manufacturer is going to tune their version of the rig to appease a certain customer base.
However the OP just installed an AT tire that's 2.5 inches taller, a couple pounds heavier, and has a stiffer sidewall than any of the OEM tire options on this platform. I'm not sure that your experience matches his goals.

-Cheers

 

I have AT tires too. Definitely don't have them under inflated though