Hi Mate
The mc18 can be hard to find parts for .some things you can do, drill some hole in airbox lid, delimit covered in the tuning section, HRC reeds ,spacers, stuffers if u get a mc21 manifold.
The best thing u can do is look through this site almost everything on here.
4 parts there are a few places that get the still avalable parts from honda japan not much left 4 mn18 though.
U can get a lot of stuff from http://www.japanauctioncenter.com/ .u can get some good stuff of there the fees are a bit high bit u can get parts cheap and a lot of second hand performance stuff that u cant get anymore.
Or go right out and put a 300 kit on it.
Have fun