For my sins I have a newish 2.0 TD Mondeo 160. I've noticed when accelerating enthusiastically from low revs (e.g booting it out of a roundabout, dry roads) the revs rise and fall like an auto box or as if the clutch is slipping. The amount of rise and fall diminishes over a period of a few seconds until the car 'hooks up' and at the same time it's making stately if unspectacular progress. There are no warning lights or weird noises the only clue is the tacho needle. In all other respects the car seems to be working fine.
I'm guessing (hoping) it's something to do with the engine management/turbo just wondered if anyone else's Mondeo does this