I had to look it up! (
http://www.m-w.com/home.htm) Loping ....
Is your speedo running OK? The cruise picks up a signal there.
Check your engine mounts also. If your engine is moving too much on its mounts, it will influence the throttle linkage. So this happen more when going over bumps and undulations in the road? (Theres a word for ya)
haasman