Winny is 17aa and obviously harder on the liver than deca. Deca should have almost no effect on the liver. If his liver values are elevated, but not above normal by more than a few points, it's probably just due to the increase in creatine kinase, an enzyme released by muscle cells in response to damage. When you work out hard, especially on gear, you damage your muscles constantly, so those levels are nearly always elevated. If his values are way above normal on deca alone, either it's not deca or he's got some other problem that needs to be checked on soon.