Originally Posted by MGM
So, the insurance company may reimburse for mods-just not go fast mods?
"recent improvements" may increase the value of your car, minus depriciation. So you just put $1000 worth of tires on your car- they might go up by a couple hundred dollars for that if you have receipts. "go fast parts", i.e, downpipes, etc, which don't increase the cars value in the wholesale market (i.e, would a dealer pay more for your car because it is FBO? No. Because it has new tires and brakes? Maybe)
Bear in mind they will use CMC to pull the asking price by local dealers on 335i's in your area with similar mileage. They did that to me, but were including non-navi cars, and cars with AT's (I only drive MT), which seemed to lower the average. I countered with an autotrader search nationwide that showed only 12 335's in the entire country for sale with stick + navi, and argued they should use that value. I also showed reciepts for a new clutch, tires, and brakes within the last 6 months. A week later they adjusted their initial offer of 21k to 24.5k.
That said, every insurer is different. For example, USAA is extremely fair. Allstate, on the other hand, has a reputation for playing hardball and being cheap. My understanding is for a long time their policy was to pay 80% of a claims value, and to make you litigate for the other 20%.
Likewise, my circumstances and experience likely played a role in my (percieved) negotiation leverage. I had enough money in the bank to keep making my car payment and to wait them out. My experience in the insurance industry gave me the ability to intelligently threaten (subtly) to consider invoking the appraisal clause of my policy, and my experience with insurance law allowed me to subtly hint at "not accusing them of bad faith in settling my total loss..."