I'm in the insurance (claims) industry and I probably wouldn't bother reporting that stuff unless I had a lot of money invested. Mods like a turbo would not be covered under the policy anyway since most of the damage to any engine parts would be considered "mechanical breakdown." (unless the car caught on fire.) If you got in a wreck and totalled the car, I'm sure you would want to be compensated for expensive mods like the turbo (so you might want to report it.) Keep in mind - insurance companies are not going to pay you what you paid for the mod. They will take the age of the item into account and depreciate it.
So here is what I would do:
If I had $1000 or less invested into mods - I wouldn't report any of that stuff
If I had somewhere over $2000 invested - I would ask my agent about it. if you have more than $2k invested and are reporting all of that stuff, don't be surprised if your insurance rates go up though. The insurance company will probably think you are at more risk of racing your car - especially if you report engine upgrades.
Between $1k & $2k - would be kind of a toss up as to whether I would report it or not.
Really.....It's all personal preference. If I were you, I would ask my agent. If the agent doesn't know, they need to talk to a claims person at the insurance company they are selling you a policy from to find out for sure on what would be covered and how it would be covered.
No insurance policy is exactly the same, and all are subject to interpretation. I am sure many personal auto policies specifically exclude "upgrades" to your vehicle. It also depends if you get a claims adjuster that knows what they are doing. If you have Progressive you might as well forget it. You would probably be better off adjusting your own claim than letting one of their worthless adjusters do it for you.
