I've had a similar problem with a 206 once when it kept dropping cylinders and ran either 3 or even down to 2 at times.
Similar symptoms to what you describe but you bloody knew it was doing it because you could hear the difference in sound, when it was running on 3 cylinders it would sound like a Subaru and when it ran on 2 it would scream its knackers off, loosing more power as it dropped cylinders.
This was down to a faulty injector, all fine after that was replaced.
Didn't think it as relevant because you didn't mention it sounding any different, but then you are a girl