induction kit works well on them but they can get a bit of heatsoak around town. the Bomz kits off ebay are well cheap.

decats work very well on the 2.0 silvertop. and the standard exhaust system is fairly restrictive.

beyond that your talking chip, cams, headers, bigger throttle body, underdrive pulley (cheap easy-ish way of releasing some horses), lightened fly, bigger injectors (the standard ones max out at 155bhp), and beyond that your talking headwork, forced induction or carbs/TB's