Modding cars for street use just isn't fun in Victoria any more. It's either make it super stealth/plain in the engine bay for the inevitable 'random' police stop, or keep your 'fast' car for use on the track. Or buy an R35 (or equivalent fast factory built car). Or move to Queensland.
The fuel pressure regulator is not a roadworthy 'defect' item, but it is on the list of 'banned' items advised by the EPA. Same goes for aftermarket ECU, fuel system mods (injectors, fuel pump(s)), exhaust, etc, etc. The EPA have authority over VicRoads to suspend your registration and impose nasty fines. Once your car has an EPA notice, you need to return it to stock, and you cannot sell it registered. Not worth the hassle unless any mods you have are easily reversible, or if you hardly ever drive it, but you still run the risk every time you take it out on the road.