not sure what pending means.. it could be that he unhooked it too soon. it may be worth your time to go to a different one and have the codes read again.
this is definitely a cat area thing especially the way the TSB is reading. seems something 91s are known for. this should be covered irregardless any warranty unless it is unrelated to the TSB.
not sure how the MAF could effect the exhaust.. hmm
anyway, look for a sticky somewhere in the garage or one of the wd21s areas, yours is basically the same. there were some pics in one of those threads at least. cleaning the MAF is defnitely worthwhile especially since it can be done in 5min.