I can only speak for VAG stuff it's in the finance agreement and part of the process of a warranty claim requires a ecu check, if the image isn't the same as stock then the system automatically flags it up . I don't think a faulty seat would trigger it but a gearbox fault would resulting in a rejected claim despite the remap not causing the issue . There was a guy on the Seat forum who fell foul of it when a simple failure caused his car to stop working , nothing to do with the remap . There have been quite a few turbo failures on Golf R's , again a manufacturing flaw but warranty claims have been rejected if the car is not stock , as these cars respond so well to a remap it could be a big issue down the line , a dsg box runs to quite a few grand