I've had a similar issue on both an LS7 car and my LS2 GTO, both with relatively mild cams. After I put the cam in my LS2 about 2 years ago, I fought this same problem using many of the same techniques that people have described here. Smoothing the timing between all the different tables helped some, but didn't cure it.
Here's a post I made about it back in 07. Although I state then that it was only a few hundred revs above idle, I've seen surging like that as high as 1600-1700. That is just not right for a 224/226 111 LSA cam in an LS2. Eventually I decided I'd just have to drive around it, as it was just a side effect of having a cam in the car.
Fast forward to now, and I'm dialing my Dad's cammed LS7 '68 Camaro. I has working on the VE with trims, when I notice a similar surging to my GTO. Looking at the logs I notice that the timing spikes correlate with Torque Management Advance on the scanner--interesting. You cans see more
here. Today I find out that these timing dips are caused by M6 Spark Smoothing. This smoothed out the LS7 this morning, so I tried it on the LS2 tonight with the same results. I was running the LS2 in 6th at 1000 rpm with no surging or bucking, almost like stock.
One more thing that causes surging/bucking on the LS7 tune is DFCO. On the LS7 it was setup to turn on basically by airflow in g/cyl, whereas in the GTO it was based on closed throttle and rpm. The LS7 would allow DFCO to start with 3-4% pedal position, so it was going on/off at those ETC pedal positions making the car surge a bit from the extreme timing/fueling changes. Changing the setup to be more like my LS2 should straighten that right out.
Try disabling the M6 Spark Smoothing.