Car is clean.
Heres my .02 cents:
Dont mod your N/A it honestly wont be worth it.
Save your money and buy a top swap kit, either find the parts at a Junk Yard or better yet find the parts here, on this website in the "For Sale" section.
Use your money to top swap your car and then go from there.
But the best idea out of them all, go turbo. With roughly $2500 you can buy yourself a Z3 Turbo kit. <------ thats the best route to go. Either top swap or turbo. Dont mod the N/A.