Paulv,
It's just a guess on my part, but after replacing all 4 O2's now and all the other CEL's gone with only the P0430 present. I can now test and pass all 4 O2's so I am hoping it's just a bad Cat. I would assume so since the PO ran with faulty O2's for almost 3 years! I'm sure the Right Cat is clogged (ruined) and the left isn't far behind.
I found a pair of good low mile cats for $350 shipped to me. The 4 O2's, MAF, 2 front tires and lots of other little maint items have left my Porsche fund a little dry. Gotta water the money tree for a bit. Meanwhile, I'm trying not to drive the car much.
Upates to come....when I get some more money.