Just Some A-hole

Hey there,

I am interested in hearing peoples' experience with tunes and downstream o2 issues.
I have an 06 Cayman S and I've recently added BB catless headers and Tubi exhaust (thrilled with the note) but am struggling with secondary o2 CELs.

Background:
No engine mods except underdrive pulley, deep sump and tune from Mase Engineering in FL.

The headers have the one bung and I added the second bung behind the rear wheels (plenty of room) with extended bungs and FabSpeed Mini Cats. It went well for about 200 miles and then I got the P0159 & P0431 for Bank 2. I cleared them (Durametric) and hoped for another couple hundred miles before reset. Unfortunately, the P0159 came back upon next drive cycle.

I'm not excited about putting the OEM exhaust manifolds back on and I am having little luck getting the tuner to eliminate the secondary o2s. At this rate I'll fail emissions testing.
Do any of you have a good tune with the secondary o2s shut off?
TIA



Pic for attention.