Are O2 Spacers required for Max-flo on 986?

[Tigger19]

Hi,
I’ve recently installed the Fabspeed Maxflo Performance Exhaust System on my 03 Boxster. It is great however, since then I keep getting error codes - P1101 [input variables charge measurement] & P1126 [oxygen sensing adaptation lower load, bank 1]. I clear the codes and it is fine for a few days, and then suddenly they are back. I do note that the CEL doesn’t come on. I only know about it as I checked with Durametric after install.
I am running a stock air filter, but not sure of the car’s history (before 2015) I cleaned both the MAF and throttle body. Suspecting air leaks, I checked for excessive vacuum on the oil filler cap, not really evident, but not knowing how long the AOS has been in – I replaced it anyway. I also replaced the O2 sensors (new Bosch). Got a new gas cap too just in case the old one was part of the problem.

I took it to an indie Porsche mechanic and he can’t find fault with the exhaust install or any air leaks either (visual inspection – not a smoke test).
I haven’t seen a P1124 code only P1126 and occasionally a P1101 (once a week).
I have seen that on some exhaust applications that O2 spacer is required. Should that be something I should try? Or given that the CEL doesn’t actually come on (runs smooth and idles fine) – is this a problem I can ignore?