http://news.bbc.co.uk/1/hi/england/merseyside/3605446.stm

All we need to do is keep a very low ratio diff to fit

Difficult one to use when you have a car which is capable of that sort of speed though.

like the low diff idea..........

Just change the diff when you get the ticket at your doorstep.

Heard through the rallying grapevine a few years ago that quite a well known rally driver employed such a technique to avoid a ban as his car suddenly wouldn't do more than 90 odd flat out.