I just recently got a 2k3 350z and i have about $1000 to put into it and i was wondering what would be the best mods for my money in terms of horsepower.

The most basic : Intake and Exhaust. ^^ for one thousand dollars...nothing much really you can do in the engine department. Need at least two thousand dollars to get something rolling...thats just my experience.

for 1k i would get nismo sways and headers if you dont want to void your warranty. you shouldnt do cai if you are planning on going FI cuz thats a waste of money. you could buy a plenum spacer, or exhaust but dont look for any huge gains from these things. g35s/350zs are hard cars to squeeze n/a horses out of.