I just got a 2003 Z400 and want to do a few little thing to it for power. things under 200$ or so
any ideas?

 

get a pro flo kit, 155 main jet, take off your lid, that will cost about 80-90$ or buy an hmf slip on for a little over $200. you can by an intake cam for like $150. Sprockets can help too for whatever kind of riding you do and there real cheap like 10$.

 

Different bars would be a good low cost mod.It go any faster but they will definitely make your wrists alot happier.........