Uh, just a warning.
My seat started doing that - squeaking, jiggling over lumps in the road. I put up with it for a while.....
until the mount point snapped and i nearly ended up horizontal when i gave it some gas at a traffic light.
Took it to ford, demanded a next day replacement (which they did) under warranty.
So: Check the mounts - they may have a stress fracture.
