Can anybody provide any advice on how best to use the electric lumbar adjustment in the front seats on the Audi A4 (& VW Passat)? I'm never sure how to adjust it for best effect. I'm assuming there shouldn't be a hollow in the seat and the passenger/driver should be able to feel the centre support (controlled using the up/down). If that sounds a bit vague, I'm even less clear how the side support works (controlled using the left/right on the control). Thanks.