i just use the autozone filters cause they are cheaper sometimes look ebay they have some decent ones i like the half circle ones, ya i removed my bumper and all the stock air duct piping, made the hole in the chassie where the existing hole was just big enough to fit the tube,
yes unfortuntly you do have to remove the bumper when you want to swap or clean the filter, one you dont have to do taht that often, two i dont recomnd this but i just zipped tied mine on, its easier to tear off and make modifactions at the track, for normal road use bolt it back in