I had the same issue, and spent quite a lot of time trying things and testing things. It ended up being one of the easiest things to try....you can go try this right now.
Take the vac line off your EGR and block it off. You can stick it on the bolt that holds the AC accumulator to the firewall, as it is close and will block off the line nicely.
Now go take the car around the block and see if you are having the same problem.
The EGR has a few common issues, one of which being a "dead spot" in the sensor. Basically the EGR starts to open while cruising, but it hits the dead spot and the PCM adds more vac to open it up further, the EGR goes past the dead spot and is open too much, so the PCM takes vac back and the EGR closes too far...because it keeps going back and forth over the dead spot. Thus the surge while crusing. With the vac line off it can't do it, and the problem will go away....IF that is your problem.
Like I said, it is an easy test that will only take a few minutes with no tools. It might work, it might not...but it's worth a quick try. It solved my problem.