Sounds to me you have one of two problems, high overall stain, or overdevelopment. Your pyro neg should not take that long to print so most cases where this occurs is due to high overall stain, which is different than proportional stain. To determine this, measure your zone I. You can do this either visually or with a regualr densitometer, remember pyro stains proportionally, so at low densities the stain is almost non existent. If your Zone I is much greater than .1 over b+f then you are experiecing high overall stain, I would recommend you dont inmerse the negative back on the spent developer. This should dimish your stain, specially the overall stain.
OTOH you might be overdeloping, using the developer too hot, etc etc...first try my suggestion, if that does not work then let me know and we will try something else.