DTC PO401 AND PO430 help

got two codes that i cant get rid of.the po401 is Exhaust Gas Recirculation Flow Insufficient Detected.so i replaced the map sensor then the egr valve both with new delphi parts,then checked to make sure the pipe from the egr valve to the exhaust manifold was not plugged and i still get the code everyday.
the po430 is Catalyst System Efficiency Below Threshold.
i replaced the downstream o2 sensor and it went away for a few months and now it comes on everyday as well.

any help will be greatly appreciated
Thanx
Ken

Bad catalytic converter? They seem to have all kinds of crazy affects when they go bad. Any power loss noticed?

no,no performance issues at all

Are you sure the EGR tube isn't leaking exhaust?

Did you check the big nut (22mm) under the EGR valve?

do you mean the big nut that secures the egr pipe?

ok fixed both codes the po430 i replaced the front o2 sensor that didnt work sooo i ordered a magnaflow catalytic convertor and welded that in...that fixed that.
the po401 code was kinda tricky..replaced the map sensor,and then the egr valve,checked the pipe from the egr valve to the exhaust manifold for blockage.that is a ll the manual tells ya to do so i googled "isuzu 3.5 dtc po401"and low and behold.there is a pipe/tube inside the intake(behind the throttle body)that supplies the egr with vacuum.it was clogged solid...cleaned it out with carb cleaner,hanger,and a blow gun.
both codes gone!!!!!

Nice work. Gotta file that one away under "OBD is not a Bible".

Any one have a picture of the throttle body removed, with this tube visible?
I've had this code issue for years. Looks like my next project.

i didnt take any pix but you cant miss it once you pull the tb away it ia about the size of a pen/pencil left and down alittle from center