My car was destroyed by fire

I live in Arizona. My vehicle was in a shop having work done. It was a 2002 Jetta. I had several modifications done to it. Upgraged wheels, suspention, exhaust, stereo, lots of engine work. The company that is covering the claim is not going to give me the money that I put into the car for modifications. I have all the receipts. They are saying they will give me the pirice that the stuff would go for if it was used. The car in the 3 months leading to the fire had been driven zero miles. This was basicly a show car. There is nothing left of the car at all. I have not been offered a loaner car either. The insurance office is also saying that when they cut a check that the money for my modifications will go towards paying off my vehicle. When I took out the loan for my vehicle I took out GAP insurance on it through VW as well. So I dont need to worry about paying it off completely. This sounds like I am going to lose alot of money. It has been three weeks since the fire.What options do I have. I have been treated like I did something wrong. All I did was take care of my can and it was destroyed by their clients and I am paying for it. What can I do? Thanks!

You did do something wrong.....

You had regular insurance on a show car.

You needed to PAY EXTRA for an insurance rider to cover all the modifications. read your policy, gee now you will.