1999 Mazda Protege: P0402 EGR valve and catalytic converter

Got the P0402 EGR valve and a tech bulletin from mazda stating this could be caused by carbon deposits at the egr outlet port , and inside the intake manifold. This may increase the exhaust gas flow circuit. My question is , could this be causing the other error codes I am getting, ie catalytic converter, oxygen sensor. I know I should just clean the valve then go and see if the codes clear, but was wondering if anybody has had this problem since a tech bulletin was put out on the part.