Re reading your post again, I would defiantly have your exhaust pressure checked. I found a muffler shop that charged like 15 bucks to test pre and post cat pressures. He drilled small holes in the pipe for his tester, then welded the holes back up. but some shops may use 02 sensor holes. My truck idled fine and ran fin to q out 30 mph. Also check the big nut on bottom of EGR, where the tube goes into the plenum under EGR.
Again, good luck