listen dude, if you went there and looked, you would see why "performance chips" are stupid. the ones you can get on ebay are 5 cent resistors, that do almost nothing. real performance chips are not needed until you start changing the compression via high CR pistons, or boost.
also on that site, if you searched in the forums, you would find that performance intake manifolds(usually polished and ported) will do close to nothing for a 1.5L engine with mild modifications.
also, if you went there, you could find that strut and sway bars help a lot with stiffening the car and reducing body roll.
also, if you went there and looked around, just a little, or even asked a question if you really couldnt find anything, you would see exactly what uk_zak posted. here, i even found it for you. its made sticky, so it remains at the top of the page, really easy to find for people.
http://hyundaiperformance.com/forums/topic.php?t=21181
there are close to no performance parts made for the x3, so saving up for a beta swap is the best way to get more power.
there ya go, right there on a spoon for you when you could easily found it by yourself.