Um - note to this:
If your cans/system are illegal for use on the public highway, they are not covered for insurance purposes for the same.
Make sure you have written confirmation from any company you insure with, explicitly mentioning that your illegal system is covered, otherwise your insurance is only fit for the production of documents at a police staion and nothing else.
My daughter (Bex) is an underwriter, and confirms that there are several companies on the scene that state they will cover anything: happy at the low price the customer pays!
Then should said customer have an accident, the company either draws their attention to the small print or withdraws their insurance as the bike was illegally on the highway.
The final twist in the coffin, is that once you have the documentation from the company, and read the small print, you will be probably be charged up to (or even over) 30% of the payment you have made - if you want the premium refunded - even before the insurance has commenced.
Sorry to be a 'wet blanket' but you must get these things clarified before parting with your money.
I'm not saying that any company mentioned on this forum is doing this, but just trying to make others aware of this growing problem in the bike (and car) industry.