For 125 the correct pressure it's: front-30, rear-33 (36 with passenger). Piaggio give's you the correct pressure, it's not a recommendation. The tyre manufacturer gives you the maximum pressure.
P.S. Check the pressure before you go, the tyre must be cold.
Sorry but I disagree, Piaggio do not make tyres and have no control over what tyres you may decide to fit on your bike. The people that design and manufacture the tyres you are using are the only ones who will give you the right pressures.
All tyres may have a max pressure on the sidewall but I'm not saying you use that, but to check and use the tyre manufacturer's prescribed pressures for your specific bike.
Also the Xevo 125 Manual (page 11) actually states 2.3bar/2.6bar, which is 33.4 F & 37.7 R as posted by MaxiSW.
http://www.scribd.com/doc/129008213/Piaggio-Xevo-125-Euro3-EN