Yes — any ECU change is a modification and must be declared. Not declaring it can void your cover and refund nothing if you claim.
Skipping this step is the single most expensive mistake a remapped car owner makes. Here's exactly how to handle it.
Bob's Mechanical Repairs — independent family-run garage in Birnam, Dunkeld, Perthshire. Call 01350 727 276 or email bob@bobsmechanicalrepairs.co.uk.