Ok to reiterate my story I used to own an Audi s2 quattro (220bhp standard trim) - insured with Elephant at the time for £500. I then delcared the following mods - engine +80bhp to 300bhp (including exhaust and remap), Brembo brakes, droped suspension, Porsche wheels. Premium remained at £500.
Then the following year, I then added my wife who had then just passed her test (ie total novice driver) as a named driver (bearing in mind this car hit 60 in 5secs!), they dropped the premium to £250.
It just goes to show.