e46 m3 is actually one big canister with quad tips.
these guys make custom quads for e36 m3s: http://www.eisenmann.co.uk/gallery.shtml
i believe they go the other route and actually have 2 canisters each with dual tips. i'm sure you can make it fit a 328i, depending on how determined you are.
i checked out the site and they do have a quad listing for 328i.