What should I do or what is wrong with vehicle?

Those are vacuum-controlled exhaust valves at the rear of the heads, are likely sticking open, eventually they'll fail and not close at all. you can replace them (very expensive, they're 600 each for parts alone), you can install a block off plate kit (less expensive), or you can remove, clean, and reinstall them. Labor is a big factor in the cost, you do have to remove the upper intake to get to them, but it's not horrible, find a reputable mechanic with minimal overhead, like a mobile mechanic who can do the work in your own garage.