On another forum we were discussing the smog fail issue w/the higher flowing cats. Since the higher flowing cats move exhaust gases more efficiently they need to operate at a much hotter temps to catalyze. Often when idling the higher flowing cats aren't hot enough, which sitting and waiting at a smog shop is usually the norm. However w/your HC's at 999, it isn't likely that the cat isn't getting hot enough, it is more likely that the cat is shot, or you are dumping a large amount of unburnt fuel into the exhaust system. You should pull the cat and see if it burnt out, it could have been bad from the start. If it looks god, have the shop test the exhaust gasses prior to the cat, if they aren't double, the cat isn't doing its job. If they readings are much higher than you have an issue somewhere else.

You said the O2 sensors were replaced using Denso's, were they oem plug ins, or were they universals that you spliced in.? If spliced you can often change the readings the ecu receives due to longer wires or more resistance.