First read this...
http://www.nicoclub.com/articl...shtml
This has been beaten up so many times that it's even funny.
The cars can be brought in; illegally, registered; illegally, titled; illegally, and driven; illegally.
There are ways to do it the right way, but it's only for the R33 models. Most of the R34's you are talking about are illegal and the owners are taking huge risks, which I am sure they probably know about. Some are Grandfathered in MotorEx cars.
You really need to read that article.