Like everything that gets older, I've noticed that the back end on my wife's V90 is starting to droop a little. In fact, when you're looking at it from the side, the rear wheel well is about 2 inches closer to the top of the tire than the front wheel well (which is an extra two inches higher). If you're trying to visualize this, image looking at the car when it's doing a hard off-the-line acceleration: the car kinda sits on its back tires a little harder. Before you give me suggestions here's what's been done to the suspension in the last few years:

Front: aftermarket swaybar endlinks and control arm bushings

Rear: Monroe shocks

Do you know if there are any bushing in the back end that can cause sag (there is nothing knocking at this point)? Or is this likely a case of worn springs in back?