I know, I think I was unlucky with my set, as have seen 803's do 377 repeatedly, on the same set of rollers, only saying don't assume, that's why I just went greys, idle and low speed running is perfect as is emissions/economy/town driving no doubt the idle stabilisation circuit helps with tickover.
Complete mapping for 3 maps cost less than £300, and that can be from a car not even starting/running.
tabetha