Raylo

I have the exact same truck and motor. The surging makes it sound like you still have a vacuum leak. Do the HVAC controls work OK? The area behind the dist is a PITA. There is a major vacuum tap in the intake manifold on the passenger side of the dist that goes to a Y. One leg of the Y goes through the firewall to the HVAC inside the cab. That operates the dampers and temp controls. The other leg of the Y has a thin hard flex tube that goes over to the drivers side of the motor to a little round thingy that happens to be the evap purge valve. That thin hard tube opens the diaphragm in the purge valve. The purge valve has 2 other main connections that communicate when the thin hard line vacuum opens the diaphragm. One goes to a hard metal line on the rear of the drivers side head that goes to the evap canister and solenoid near the fuel tank. The other connection goes to a hard flex line that goes to vacuum tap just under the throttle body. It's easy to dislodge any or all of these while futzing with the dist. Plus some of the lines can be cracked with age. And don't forget to check the PCV line for cracks.

I've not heard of CPI causing surging but I guess it's possible. The upper plenum comes off pretty easily and you can look for "clean" areas near the incoming plastic fuel lines or the FPR for signs of leakage. Fuel can leak here and cause problems. You'll probably need a new plenum gasket... typically carried at the local parts places for $12-$15. Also, it is much easier to get at the vacuum lines back there with the upper plenum off.

Oh, when you cleaned the EGR I assume you also cleaned the pintle and seat in addition to the mating surface and ports. That is essential to get it to seat properly.