well-- i dont know what to suggest.

the thing is that there are many other cars that offer more for your money, if you are just trying to speed it up a bit you are on the right track, but the D-series isnt really anything special and you probably wont see much of a difference--

the only ideal modification would be to swap it out for a b-series, i'd suggest a b20 because it will give the car a considerable kick in the ass over the d-series and still afford a good ammount economy