Without trying to sound partonising if your talking about super/turbocharging its not going to make insurance any better more likely worse if you start modding and if you dont tell them then whats the point in having insurance at all as they wouldnt pay out. If youve got the money take it to a reputable tuner and im sure they could do something with a t28 but for the money you could buy a newer 1.8t or v6 and chip giving you an easy 200+bhp and pay the higher insurance. Ive thought about modding mine(2.0) with a supercharger but its really not worth it for what you gain although much rarer, so im waiting for a years no claims and a bit more money to get something more powerful.