Even bog standard a remap on a modern diesel shows some difference! Both in power and also higher mpg in most cases. Start ripping DPFs, EGRs, swirl flaps etc and turns diesels into animals. If its mapped right, ie on a dyno then should be sound. If some cunt came round the boys house with a samsung tablet, a usb and a tuning box then those kinda generic maps are gonna be the ones causing harm id have thought.