Exclamation [Q] [PROBLEM] In-game lag spikes.

Hello. Recently i bought Xperia Z. Kept using stock kitkat OS, but decided to downgrade to 4.3. Now the problems is- a lot of games that i play have decent lag spikes. Games like AVABEL (mmorpg) runs smoothly for a few seconds and then lags, then again. Googled a bit, it seems that this game runs perfectly for others. Other games (like The Infinte Black) run at 9-10 fps, while on four times weaker Xperia Play i played at a decent 24 fps. I have about 4gb free storage space. Any ideas what might cause this lag?