What's Wrong With This Camry ?

05 Toyota Camry brings out vapor from the exhaust at cold start, but after it warms up particularly after driving a few miles, it rattles which was linked to timing chain slacking, release some smoke during hard acceleration and eventually short oil. It also finds it difficult to climb hill. I really can use AC too as it will idle roughly. Recently changed the oil from Mobil xhp 20w-50 to mobil 2000 5w-30. Also clean it's clogged PCV valve Any recommendations to mitigate this or a mechanic around Lagos that could work on this. Thanks