turbo insurance?

I'm planning putting a turbo on my diesel truck in the summer. I know there is a few people who have this conversion. Iwas wondering what sort of difference it makes to ones insurance? I'm already on a modified vehicle policy cos of my lowered suspension and aftermarket wheels. I seem to remember I pay abour £240 at the mo, I'm 35 a teacher, clean licence etc. I'm only plannng a basic conversion, not a screamer.