Aftermarket parts

Togo

Well if you are looking at the "big players" as companies like Greddy, HKS, Tanabe, etc, they are going to be supporting the Z34 platform but haven't released a whole lot as of yet.

There are a couple posts floating around of a Greddy exhaust system to come out in the near future as well as a Twin Turbo setup. Their twin turbo was one of the most popular kits released for the 350Z and should have a huge following on the 370Z as well.

HKS has some drop in filters that I've seen as well as a short ram type intake but I saw it listed somewhere for around $700-$800! I'm not sure the gains from this intake will be worth $200-$300 more than Stillen's G3 if their are gains greater than the G3's to be had. HKS also has some axle-back exhaust system currently out with rumors of one or two more to be release some time late this year.

Tanabe had two exhausts that were leaked out along with some springs and other suspension goodies.

Hope that helps. I'm sure there is more out there that is being developed and will be released soon but it'll just be a matter of time. I'd agree with the above posts though, you can't go wrong with the Stillen G3s and some Berk HFCs. You might also want to consider doing a Stillen UD pulley. There are some good CBE out already, and you aren't going to see higher gains months from now from a CBE compared to what's being gained now. If you see a CBE you really like now, go for it.

Helpful Links
Greddy Exhausts
proto Greddy Ti-C exhaust...sexy dual 2.75" goodness
Greddy TT Kit
Greddy Twin-Turbo In Development
HKS Intakes
HKS Racing Suction Reloaded Kit Nissan 370Z
HKS Exhaust
Venaci 370Z @ the Track Drifting!
Tanabe
TANABE Racing development 370Z update: TANABE springs, swaybar and underbrace
Tanabe R&D was updated
TANABE Racing Development Exhaust for 370Z: TANABE Medalion Touring Exhaust