the EGR doesnt cause a overrich condition. unless it malfunctioning was causing misfire type conditions
my guess that there is a possible exhaust leak,
or the TPS is tripping like trav and i talked about.
Oh there certainly is a bit of an exhaust leak! But it is quite a bit down stream of the O2 sensors, but you cant ever second guess old school japanese magic.
Wouldn't the ecm in limp mode cause by any error code run rich? Independent of what caused the code? Just my curiosity
Matt