well a couple of things, by doing these so called stage one mods, you will gain nothing, by putting a fart can you will feel like you have a rocket but if you see the times they wont be that different....
if you need some signioficant figures than either an engien swapi.e. k20 or put a turbo or some thing like this...
but i fail to understand how much poweryou need, its already 140 bhp, good enough for a sedan, and instead of wasting a couple of 100 k's on mods and ruinign your expensive car, i.e. eliminating the reliability and peace of mind... you could get a stock fast car like rx8 type s or evo or something like this