This seems like a drivability issue to me. THe weight/gearing/vs engine management/design I do not have a tach but I suspect mine has a slight "Buck" at that rpm as well and while I don't believe it should do it, but it is easy to fix, just downshift.
One thing I have thought of is since all SVXes were automatics the engine management system may be a factor at low rpms, it probably expects the tranny to downshift itself sooner than you are manually downshifting. I have always thought of engines and trannies as separate animals but these modern engines seem designed around each other. This engine may simply not be designed to lug around a van at those rpms.
I will watch with interest to see if you find a different solution, but I don't think you should be in third rounding corners in the neighborhood. Of course r and p, tire size and gear size all contribute. I don't usually put mine in 4th until about 60 mph!
Neil
