Althought what I say goes for insurance in CA, You wont really ever get an insurance company to cover racing parts like Turbos and Maintenance upgrades because it makes the car more and more poised to fail.
Anything that would fall under Performance Aftermarket you are SOL
The only thing insurance companies would think about covering if you have the correct documentation is aesthetic parts like a body kit and/or aerodynamic aesthetic parts.
The correct documentation being;
-Past Paid Receipts/Invoices for Parts from Vendor that MUST still be in business
-Past Paid Receipts/Invoices for Paint and Labor and Fitting from Bodyshop that MUST be still in business
If either are out of business you are SOL.
Even if you have all the documentation and work in the insurance industry like I do, and know all the same rules and regulations as the insurance company, like I was dealing with it is still very hard and difficult to win these bouts
if you want some more info, click my build link below and go to page 12 and read my entire breakdown of what happened with my insurance company.
Birdman's Build