Pirelli P Zero Rossos Tire Pressure

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Hi kids, haven't been around here for a while but thought I'd bounce this off you.

I have Pirelli P Zeros all around (225/40 front, 265/35 rear). I noticed a lot of wear on the rears and took the car to America's Tire where I bought them to see if the wear was normal. I was told the tires were wearing a lot in the center of the tread but not very much elsewhere, indicating the tires were over-inflated. The thing is, I kept the pressure at exactly the pressure recommended by Porsche.

I've deflated the tires a few pounds in hopes the tires will last longer. And the car seems to corner a bit better as well.

So who's right about the tire pressure, Porsche or America's Tire?