Welcome! As Ken said, there's a ton of different routes you can go as far as upgrades go. Performance-wise, the FX35 is pretty dead-ended in naturally aspirated modifications. The 350Z guys learned years ago how awfully painful it is coming to realize how little power they get compared to the high dollar spent. There's been Z's (we share the same motor, FYI) with over $10,000 invested into the motor alone that barely broke 300 wheel horsepower, and then twin turbo stock block Z's who easily broke 400 wheel horsepower for $8,000.
But if you'd like to upgrade/update the '04 FX you have, there's a member here that goes by the name turbocad who has transformed his old-school FX into one that can be easily mistaken for an '08.
