Bouncing rail pressure and cruise control

[Tinman]

I've had a unusual feeling while using cruise control. After the truck crest a hill, it'll surge slightly kinda like you have a trailer behind you. It last a few seconds then smooths out. I finally noticed this weekend that the cause is the rail pressure will bouncing up and down. As the cruise backs off the throttle to coast down a hill, it seems to stop at about 10500 psi. This is where it will bounce up to about 11000-11500psi with a frequency of about 1-2 a second for 2-3 seconds. It's annoying. I can't reproduce it with my foot, but my foot acheive a exact rail pressure either. I'm thinking FCA. BTW, it does it with the smarty sw or stock sw.