1996 Ford Taurus • 94,000 miles

I've been a mechanic for about 15 years so I have some experience in diag. I've been trying to diag a problem with the car surging, and its not a misfire. It started as an EGR code, I've replaced the egr, both vac. Solenoids and am having the problem still. When I unplug the EGR the problem goes away, so thats what led me to believe that the solenoids supplying the vacume were bad? All the specs for the sensors are correct. I'm skipping through the minor details so I dont bore anyone, but my question is has any carrier or experienced mechanic had this same problem?
May 3, 2013.

If you had a 401 code, replace the dpfe.

Check the back pressure on the cat converter. It may be backing up into the egr.