This mods im gonna list its not particularly for neo,its more like general mods that you can look into.
-Open pod filter
-racing clutch,lighten flywheel.
-lighten crank pulley
-4-1 extractor
-a better flowing exhaust(bigger..if your car 1.6,i think 1.8" is enough)
-port & polish your head
-adjustable cam pulley(then you can decide to advance or retard your cam,depending on what you want out of your car)
If you have the budget(provided you dont want to tranplant your engine) you can bolt on turbo.
If you need more info in depth about modding the internals such as pistons,bores or stroker kits,better ask the sifu's.