Finally got around to changing the CVV on my 540 and can happily report it fixed the problem with downshifting. For quite some time the car would not downshift properly and it appeared to be temperature related. It was very annoying having to get into the floor switch all the time because this caused a downshift of two gears when I only wanted one. As best as I can tell, the CVV diaphragm was bad causing enough of a vacuum leak to screw up the "load" signal to the ECU. Worse when warm.

For anyone else with downshift problems, try the CVV before expensive transmission work. BTW, the CVV on 540's is a giant pain to work on, be prepared to die grind the screw heads off.

1998 540ia