Wife and son both have Jaguar XE's with same engine, however different power outputs, so hers is £30 a year road tax his well over £100 a year. There is nothing when riding in the two cars which makes one realise one is much higher spec to other, they are just both nice cars. However reading the caravan forums it seems specially with VW people get the software changed to give them more power for towing, to my mind that if fraud, unless you declare to the government what you have done, however before the road tax changes it would only be the insurance company you needed to tell. However in the days of the twin carb it was easy enough for the buyer to see engine changes, but with a software change there is nothing the user can see, so one may have a car which has been altered without knowing, or you may have altered the car and claimed you don't know. So on buying a new car, should one get the software tested? As even if it has been altered your unlikely to have a problem unless there is a fatal crash only then would anyone look.