My throttle body leaked a terrible amount, enough to notice the car running extremely rich under boost once the air started to leak out and the fuel mixture became incorrect.
Hypertune of Australia produces an all billet throttle, 66mm ID, features sealed bearings, and is available in any anodized color.
Here is the throttle with the KA24 TPS adapter installed, which is the exact same TPS that the VG30E uses. (The adapter can be clocked in any direction, for fine tuning, along with the regular adjustability of the TPS)
If you are interested in acquiring a Hypertune throttle for your Z31, you can contact John at Affinis Motorsports, https://affinismotorsports.com/
Make sure you ask for a 70mm (SR20 / KA24 / RB30 Bolt-on (Now for VG30E!)) throttle body with a KA24 tps adapter.