However if the mishap is not result of the remap any insurance company would probably have a very hard time trying to wiggle out of a claim. Insurance companies are not bothered with a tow bar fitment which could add value to the vehicle plus it is a physical modification. After all the insurance is based on the value of the vehicle and not the driver's abilities.
If an insurance company wanted to 'wriggle out' of a claim with regard to a vehicle that had been modified in any way and they hadn't been informed about the modification they would have no difficulty whatsoever.
When an insurance policy is purchased the insurers will provide a statement of facts.
This statement gives the correct details of the vehicle and driver(s) that are covered by the policy.
The insured is asked to check the material facts and to correct any inaccuracies before the policy is issued.
To conceal any fact, and this includes modifications of any kind, would be deception.
Insurance is also based on mutual trust, and that trust involves disclosure.