EGR valve testing

[truckin 79]

I have failed CO emissions test twice and have adjusted idle mixture screws the second time around. I replaced all filters, air, crankcase and canister. It did help but still high HC and CO are way high to pass. I am starting to think either cat or egr might be the problem. The truck does run well for the most part. I can press down on gas pedal pretty hard and truck does not do much. I did stomp on gas pedal and could hear secondaries open up but still no wow affect. The truck is a steady performer though, if I just give it a little gas it will accelerate fine. On a side note what is the temp on cat? I have a temp gun and it was about 350 degress when pointed at cat