Thanks Kaz for your thoughts.
I fitted the HKS unit in the loom before the ECU using the Japanese instructions and a Japanese NSX friend who translated, unfortunately it still is restricted. So that didnt work! I was going to temporarily swap ECUs from the Australian car into the JDM car to see if that worked on speed limit and cruise limiter, but the JDM car has 4 O2 sensors and the Aud car has 2 O2 sensors so thought that wasnt so smart.
Does anyone know which ECU from a USA car would work in the JDM car? I guess a DBW with 4 O2 sensors but think the USA CARS are OBD2 and the JDM is OBD1 for that vintage.
Thanks,
Scott
JDM 1996 Monte Carlo Blue, Coupe, Manual, Black roof, Man steering. All original.