My insurer is a specialist one, which, understands that many people have vehicles with mods that are not engineered on them from Hi performance street cars, to custom hot rods, chopper style motorcycles, track/rally spec cars etc. If one of its clients makes a claim and the vehicle is fitted with un roadworthy or non engineered mods BUT that mod/s is NOT the CAUSE for the claim, then generally they will still pay out but if the assessor can prove that the illegal mod was the reason for the claim then the claim can be declined...