I did it with my CL9 all by myself. I bought a HKS SLD Type-1 online. It comes with wiring diagram but its in Japanese. It also contains a English one but its generic.
I scanned the wiring diagram, used google translate and wallahhh !!! wired it with my ecu. Tested it on motorway at 210km/hr.
However 2 things i would like to share,
1) Your speedometer will now stop at 170 km/hr. So you would need to check your speed on third party device. I used my HTC Desire which has a accelorometer sensor and can give you speed.
2) Your curise control will still be locked at 110km/hr. I believe it can also be unlocked but using HKS SLD Type-2 (12 wires, A/T models, more complicated than Type-1 which has 5 wires).