I know this one has been covered before. I searched and read previous posts on this including how to test both the EGR valve and modulator. I'll do that when I get home tonight. My question though is this:

After getting cel code 71, I cleaned the EGR sensor and the modulator (filter element had lots of carbon junk) and the error code hasn't come back... yet?

I took the truck to get smogged and it failed the 25mph test, too high on Noxx. Anyways, I noticed that it idles at 1000rpm in gear, and 1200rpm when in park. I know both are high, which makes me suspect it's the EGR valve, however what accounts for the difference idle speeds?

What should be the order of replacing parts? The smog guy said check timing first, then EGR valve, then catalytic converter.