The Consumer Insurance (Representation and Disclosure) Act 2012 removes the duty on consumers to disclose any facts that a prudent underwriter would consider material, and replaces this with a duty to take reasonable care not to make a misrepresentation.
So that protects you when you buy a car that has been modified in some way that you don't know about. For example, many cars these days come with a turbocharger, how are you supposed to know the one you are buying has had an aftermarket turbo fitted? Obviously we do, but the ordinary person in the street who knows little about cars who eventually buys that car may not. .
In other words, a previous owner may already have done the 160 remap, and not told you . . . so you can't have a duty to tell the insurers if you don't know about it.
So maybe the previous owner of your car did have a 160 remap and not told you?
Ali.