I'm an insurance broker ....... I have my sleds through Farm Bureau and they will allow for power adders like that but you need to provide detailed reciepts and pictures and they assign additional value to the sled to cover the parts ......
CONTINGENT UPON ....... no racing, speed events, etc.
Farm Bureau does not do business in WA to my knowledge ..... I think that you would have some luck with some of the following national carriers .......
The big thing with most of the companies is good documentation and pictures of all your aftermarket goodies and reassure them no racing of any kind. I'm not sure of all the companies guidelines off the top of my head ..... You'll just have to do some checking ..... Start with whoever insures your cars.
Too bad you don't have Farm Bureau ........ They insured my turbo'd zx10 crotch rocket for $570 a year with $250 deductibles