[Q] Lag on Xperia Z 4.3 topic

Hello Xda. I have a Sony Xperia Z, stock rom, locked bootloader , non-rooted and with android 4.3 (10.4.B.0.569, Belgium version). All of my games lags on this device ( asphalt 8 , subway surf, even fruit ninja sometimes). Except games, nothing lags (menu, transition between apps etc). I tried many of the 10.4.B.0.569 build versions (singapore, switzerland, australia version ) but nothing changes. Strangely is that on .267 version the menu, album, camera was laggy, but not the games. Anyone knows what can I do to resolve the lag problem? (root or changing the phone from stock isn't an option, because I don't want to lose warranty).