I woudl start by telling us all what is causing the tuning the place to say that there is a fault with your AFM?
I would try giving it a good clean first. (use electronics contact cleaner, just give it a good spray. Dont touch the spring with your fingers or anything though.)
If it is faulty, buy another stock rb25 AFM from the for sale section (cheap). Then the issue should be resolved. As stated earlier, a Z32 AFM requires an aftermarket ecu or ecu retune/flash (not sure if anyone in perth can do it yet), and is not really needed until you start chasing 220-300rwkw anyway.
Good luck