Exhaust & O2 sensors- work around ?

[NickySB]

Hi Everyone

The flanges on my original exhaust were rusting away so I opted to replace the entire system ( exhaust manifold, centre pipe & back box ) - due to cost I opted for a pattern system.

As soon as the work was complete the GS (450h) started generating the P0420/P0430 codes,  I suspect due to  substandard cats in the centre section ( not OEM). I’ve tried various roots to resolve (new sensors / spacers/ confirming no leaks etc ) and it still won’t stop generating. A check on TechStream confirms the sensors are working fine but they’re outside the tight margin in the current set up. I’ve not found anyone who can manage to open the threshold on the ECU settings.  Emulators for the 450h don’t exist so I’m running out of options other than replacing the centre section with OEM ( current list price £1340.06) - has anyone else come across the same and found a work around ? Does wiring a resistor into the O2 sensor resolve ?

Thanks 

[Linas.P]

The main cats are on the downpipes before the flange, the cats on middle section are secondary and strictly speaking not needed, there are no sensors after them either. So whatever is causing your issues would be upstream. Not that it helps you at all as the manifolds probably are not much cheaper than middle section.

[NickySB]

OEM exhaust manifolds are IRO £654 per side. 
As I understand it, the sensors in the manifold are air fuel ratio sensors. I am not particularly suspicious of those because the car is running well, still achieving 40mpg and they’re situated before the cat on the manifold, so I guess yes, it can only be the manifold cats

[NickySB]

went back to oem exhaust manifolds and fault resolved