do not just remove the whole end cap, what can be done is to pull it, look at the inner most tip of the tube, there is a cone shaped piece on it that is supposdly the spark arrestor, that can be cut off for more direct flow, but nothing you can do to a stock silencer is going to give you much if any gains.
even adding just an aftermarket silencer may only give a very slight gain, the only real gain is with a full aftermarket expansion chamber/silencer and rejetting