by the sound of it it is a fairly stock bike.
Without spending much I would do the following.
-Get tuneECU and a cable.
-Turn off the 02 sensors (with tuneECU)
-make sure the TPS is adjusted correctly (tuneECU diagnostics mode)
-make sure the throttlebodies are balanced (again can be done with tuneECU)
-if you are confident enough to remove the secondary flies and shafts do this and also turn off in tuneECU (those who dont agree with this mod tend to have never removed them in the first place; however it smoothens the throttle response as there is not an extra set of butterflies moving independantly of the ones cotrolled by your right hand)
-while at it with tune ecu you may as well turn off the 2nd and 3rd gear restricter
-as you have the stock exhaust DO NOT REMOVE OR TURN OFF THE SAS, this is required to keep your catalytic converter clean and free flowing (as much as the stock exhaust can be anyway)
next step towards smoothness requires a fair amount of money and includes a motobox or equivelent and there is not much point in doing this without the exhaust.