No 4 cylinder needs dual exhaust, period. If I had an s2k I'd get an aftermarket system with a single outlet. It adds weight and probably won't give you any gains, if anything you might loose power. I've heard the N1 is very loud. Look at an RS*R system or something similar, there's a couple other good ones. I'd just leave you stock spolier alone, same with the antenna and rear wiper. The rear wiper is a nice to have thing that helps you see there is no reason to get rid of unless you are building a show car. There's no reason to get rid of the cruise control, it won't save any weight. I'd stay away from a short shifter, as long as your transmission is in good shape, doesn't have much play, and the car is going to be used on the street you really don't need it. It's easier on your syncros and when the transmission does get worn as they tend to do when driven hard, you'll be less likely to miss a shift and overrev, and you'll be less likely to misshift anyways. I've never seen the point of tint and it usually looks like shit when you DIY but that's your preference.

Motegis are shitty heavy flashy wheels. Look at some rotas that are light, tasteful, and similarly priced. Don't bother with a clutch unless yours is worn out.