Our 2000 S80 T6 came with MXM4 Pilots H rated (sustained speeds up to 130 mph). Although some Volvo drivers may want V speed rated (or even Z) tires, I'm not of the opinion they're needed.

Noting you used 32 psi in the original Pilots and now use 28 in the V4s, the 4 psi difference is enough to make the V4's produce a softer ride - assuming both types have similar construction and sidewall bulge for a given pressure and weight on them. Our S80 ran a bit rough with 33 psi all around in the MXM4s and also had insufficient wear at rear tire tread edges and a bit much at the center. Plus the contact patch wasn't all the way out to the mid-radius point where tread meets sidewall; the place our tire dealer says it's supposed to be for best safety and comfort. I now keep 33 psi in the front and 27 psi in the rear tires (rears go to 30-31 psi when back is full of passengers and luggage). Much more comfortable and getting very even tread wear. I know, 6 psi difference between front and rear seems a lot, but when so set, the sidewall bulge is equal for all tires; there is more weight on the front tires than the rear ones.