A high powered car needs good cooling, especially on the track. The stock bumper has a decent sized grille, but no side vents for oil coolers or brake ducts.

All the kits out there for the 350Z look absolutely disgusting, with the exception of the plain Nismo kit. (Nissan's S-tune "GT" car is definitely among the worst though)

The only bumper I've seen that is even remotely decent is the top secret bumper, and the Fiber Images rip off of the TS kit that Cheston has on his car. If nothing else come up, I suppose I will have to go with that one.

Similarly.. what about hoods with proper venting? I've only seen one or two, and they're all fairly ugly too.

I'm not sure what drives the design of these ugly body kits. There is nothing cool about these kits with lots of fake vents and grilles all over the car -- they only serve to disrupt airflow and ruin the proper aerodynamics that Nissan engineers tried very hard to achieve.