What would the insurance ramifications be for adding a turbo charger to a 130HP Mitsubishi Lancer?

First off, to add a turbocharger "legally" the entire turbocharger unit and assembly must receive a C.A.R.B (California Air Resources Board) approval number from C.A.R.B or another similar group for your state. Secondly, a good amount of the insurance amount would be determined on a per-policy basis - I would have to assume.