Bruce, I understand (know) it is possible to fit a unit external to the ECU, which requires splicing into 3 wires, you should be able to find the info online on this.
It does not change mapping, only removes the speed limit so it will go to 160 KPH.
Take a look at 'HKS Speed Limit Defencer - Type 1' you just need the correct wires from ECU, I think 12v, earth and the speed sensor, you also need to set the dip switches for honda.