Andrew, thanks for the advice. I did as you suggested and switched the solenoids but unfortunately no change in symptoms. When I first started it after the switch, Bank 2 oscillated between -19 and 41 but once it warmed up a bit, it stayed on -19 again.

Now that the actuation and the sensors are no longer a consideration, I have to think what might be wrong with the mechanical items. The Vanos units were tight after I put the new seals in but not beyond reason. I replaced the rectangrings and the check valves. There should not be a major issue with either of those. I guess I will have to lift the driver's side valve cover to see what is going on with the timing.

I am about to get a Foxwell for the Cayenne, looks like I should get the BMW software as well.

Unfortunately I am away for a few weeks and it will be a while before I can get back to this problem.

EDIT: I checked my pictures of the timing and the timing looks in order. I wonder if the check-valve could be bad? If not I will have to take the vanos off anf check the distribution piece as well. Could I have damaged the Vanos seal when I installed it and have a loss of pressure? Will add pics a bit later.

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2003 4.4i black ext./black int./black headliner (kid's runabout)
2014 535d X-drive, M package, silver/black interior

Sold but not forgotten:
2009 E70 35d, black ext./black int./black headliner (sold 2021)
2006 4.8iS Le Mans blue/cream int./black headliner, SOLD in 2012 sadly...

Other hardware:
2015 Cayenne S (wife's new DD and definitely wroooommmmm)
2016 Tundra 1794 edition crew cab, luxo hauler
2005 Tundra crew cab, weekend hauler. Sold after 150k very happy miles.