You will get tiny, probably un-noticeable, performance increases through things like an induction kit, catback exhaust, decat, etc.
For any serious increase you're going to have to go down the supercharging (e.g. very easy to install TTE kit if you can find one), turbocharging (typically very complex) or engine swap (e.g. 3S-GTE, 1G-GTE, 2JZ etc) routes.