Is this Bardhal good for the bike? The svc guys told me that it makes the engine smooth and increases the mileage.

That characteristic power delivery happens to pulsars if one of the plugs is fouled(the one on the right side). Since your engine have burned 2t, there is a larger possibility for your plug to fowl so please check the right side plug. U can use ur tool OE kit. Go for any kind of additives only after this check. Additives are not prescribed by any manufacturer.
Fuel injector cleaner is used for de-carbon and also removing salt formation due to prolonged usage. Either of this would not have happened to your engine since the vehicle is new. So please do that check first.