Some time ago I designed and 3d printed an air filter for my BMW. It worked wonderfully.The intake noises are like a sports air filter.Also fits other vehicles with a connection of 70mm.I used a commercially available filter mat as the filter.
STL (Stereolithography, filesize: 9.9 MB), OBJ (OBJ, filesize: 7.66 MB), 3MF (3D Manufacturing File, filesize: 2.66 MB)