Long story Paul.
That is a characteristics of the hadex system in that it has to detect a small amount of slip before the rear wheels join in.Since my remap , Been out twice in my car, York to Leeds , when I put my foot down the front wheels spin , The all wheel drive comes in, But takes a few secs ????
No map on mine but apart from a quick skip on a loose footing it feels nothing but planted and sets off like a scalded cat!To add , Pulling out on a fast road my car struggles with traction up to (the speed limit) ??? and a bit, The traction light flashes on dash.