My 13 XSport inflation recommendation is 35PSI, and that's what I run in mine (regardless of tire brand). Keep in mind, the maximum tire pressure on a tire sidewall is for use at the maximum load rating. OE tire pressures are based on your vehicle weight. The exact same tire installed on a vehicle of different weight would have a different inflation recommendation. If you are heavily loaded with cargo or heavy tongue weight trailer, you may want to air up your rear tires for the added load, but for normal use, use the recommended pressure on the sticker inside your driver's side door.
Over-inflating the tire will cause premature center wear and reduce your traction in all conditions. Under-inflating can cause outer wear issues. Is outer and inner edge wear both excessive or is one worse than the other?
EDIT: I have Nankang SP-5 tires on my XSport now, and they are the worst tire's I've ever had. They only had 500 miles on them when I bought my truck new, so it seemed wasteful to buy a whole new set. One of them already had a broken belt and needed to be replaced. I'm going to wear them down and replace with Michelins when ready.