[batou]

I told them BEFORE taking out the policy that I was modding the car over the period of it's ownership and that I had already done the supercharger pulley.

Although the pulley is not covered if any insured parts are damaged by an uninsured part they will pay out. If for example the pulley failed and ruined the supercharger then they would replace the supercharger, pay for labour just not the 50 or so quid for the alta pulley.

This is on my policy documents.