As far as the insurance goes, yes, if the insurance assessor finds out then you could be in trouble. However, it is incredibly difficult to find out as the only way is to compare the map to one on an unaltered ECU. Tecnically you are not changing any of the part of the car. You are just altering its function ( Fuel ratios, timing etc) http://www.angeltuning.co.uk/ai_faq.asp#9