elf, aren't you running Ecutek? Can't you shut the CEL off?
Yes, I'm on ecutek and I also have stock downpipes
We're having the issue on my wife's car which is Cobb tuned and has catless downpipes. Previous owner had their shop add little extension tubes about 3-4" long so the second O2 sensor isn't directly in the airflow through the downpipe, it's a little bit delayed - however that hasn't totally solved the issue.
I only looked at her exhaust once right when we got the car but it seemed to be very difficult, maybe even impossible to reach the second set of O2 sensors without removing the downpipes. I'll check it out again next time her car is at my shop.
2010 GT-R - Matte Gray, AP/Carbotech, BSE trans cooler, BSE tune on ECUTek, H&R sways, AMSOIL, NASA-AZ TT2 and occasional DD
1976 FJ-40 Rock Buggy - tube chassis, LQ4, 700R4, NP205, Rockwells, F&R hydraulic steering, Fox, Ballistic, lots of 4130, 7068, and AR400
2001 Ford Excursion - V10, DD and occasional tow rig
Do want someday - Radical, 599 GTB w/FHP, 430 Scud, Superlite Coupe, FF Type 65 Coupe