07 GSA brake surging

I recently bought an 07 GSA with 18K. Both front & rear brakes have a low speed surge/pulse. The rotors were replaced under warranty at 10k. I read a suggestion to sand the rotors for pad residue. This fixed about 50% of the surging. Any suggestions on aftermarket pads to deal with this or do I need check runout on rotors next. At this point it's a small annoyance, not a safety issue. Braking is completely smooth until about 20 mph. Just wondering, I can see an RT needing stainless rotors but wouldn't a GS look better with rusty cast iron rotors??

My 07 RT has this problem. It's now reaching "safety issue" level and I'm replacing both fronts and rears soon. Solid mount rotors that warp suck.

Hi Steve, Are you on original rotors? There is another thread concerning this you want to read. One of the suggestions is don't replace rotors & pads together.
fred

I may have seen it but if you can post a link, it would be helpful. Fronts are original, rear rotor was replaced 40,000 miles ago but now needs replacing again.