congrats man! it honestly depends on what you’re going for. If you want good looks, then do good looks things (lower it if youd like, i got an si spoiler for the oem+ look, wheels, etc). As far as power goes, from what I understand the r18 is kind of not the best option for going fast etc, most people say the ECU auto adjusts to maintain the same power. if I were you and I did want just a little more power, I’d do exhaust (borla makes a nice axle back for around 400$), get a flashpro, then go from there. Keep us posted on where you go with it!