Hey bro, do u mean drill holes on the stock air-box? If yes, the hole mus be wat size?drop in is good for city drive... but spirited drive is abit less enthusiastic compare to open port... it doesnt give u the open port roar sound.... high rpm feels a little bit restricted compare to open port.....
both filter element is the same.... what makes the difference is ur oem airbox... by using open port air filter, u dont need ur airbox... air flowing to ur filter will not be restricted....
as in drop in filter, u still use ur oem airbox... air flow is restricted by the size and shape of ur airbox air inlet....
there are more creative methods modifying ur airbox... drilling extra holes to compensate the need of high flow at high rpm... yet u still enjoy the cheaper drop-in air filter and oem cai intake that comes with ur car....
Thanks!