hey man read through this link below if u have sometime... I've had the same 2 codes for 10+months and about 11k miles... I've done so much to try and get ride of these its not even funny. Look at what all i've done maybe this can help you. I think it to be an exhaust leak comming from the exhaust manifolds to the heads or that could be masking the real problem... havnt had the time to replace the gaskets but when i do i hope that to fix the problem... If you have any input that would be great. Well either way i just figured this would help u out alittle...
Jason
http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=trouble&Number=1158957&page=3&view=collapsed&sb=5&o=7&fpart=all 
