Do anyone knows if you can cut a wire so you don't have any speed limit, Sorry for my bad English but I hope you understand, I know that on the skyline you can cut a wire.
I wouldn't suggest it. The S15's combination meter is so complex that stuffing about with it could stop one or more of a vast number of electrical systems from working. I believe it's an ECU tweak to remove the 180kph limit. Fitting a Power FC is one way, a Nismo 280kph combination meter is another. In the UK, fitting the mph converter is enough, as this raises the 180kph limit to 180mph.
There are lots of electronic boxes from various tuning companies you can fit to remove the speed limiter.
I had an Ultra digital speed meter in my old S15. But Blitz, Greddy, HKS etc all make boxes which remove the speed limiter.
I would look into a tunable ECU or piggyback though and get a remap done and raise the boost over 0,8Bar