pug 206 diesel odd running

[pesty]

Hi, I am baffled - have 2002 peugeot 206 1.9 diesel. At low speeds it misfires, stutters rerally bad press accelerator or lighten off accelerator and all is well again. Its worse is when in a high gear and cruising slowly around 50mph, again alter accelerator pedal pressure, either way and it clears, you have to either slow down and change down or speed up to clear it, hard to describe.
Plus, this morning on a cold start the revs dropped right down almost to cut out then picked itself back up - done this a couple of times then ok ?
Any thoughts / ideas appreciated....

[imajenarry]

sound like you may have air in your fuel system, or a blocked injector.