I do wonder sometimes whether insurance companies would even notice things like this....
....Possibly not your average insurer but if you have a specialist like Greenlight who
ONLY insure modded cars, and who literally cover like-for-like, then they do employ assessors who do know all about mods (even how a car is fuelled).
It's more in your interests to declare mods than not to do so on such policies. They don't up your premium but during your annual cover period they'll make a charge to cover their work in updating the policy with additional items, which I think is fair enough when their premiums are so low compared to others.