Help please? 2004 Xfr with manual trans and 53,000 miles. Car runs FINE - no starting, performance or mpg issues whatsoever

Had the P0410 codes 2 years ago (Jan 2014), pulled & checked RCM (a-ok), air pump worked fine, replaced the small blue check valve and was all good until Dec 2015 and code reappeared.

Air pump is working properly (on when cold then shuts off) and RCM, ground wire & blue check valve all good. Took Xfr to a local MBZ shop I know for years and after two days they recommend replacing the two upstream o2 sensors ($676) as they may be "lazy".

Anybody ever heard about this as a P0410 issue? Checked online found the Bosch 16167 o2 sensors at $67 each plus cost of a special socket for removal/installation.



The problem is the car rego is due now (got a 60 day extension) but having read all the threads (secondary valves, carbon build up in intake tubes, etc.) I fear I'm headed down a rabbit hole now.

Any help is appreciated.