Vauxhall Astra mis fire when cold

First thing in the morning the engine will start first turn of the key no probs,and will also tick over and idle no problem,there seems to be an eratic moment when revved between 1800-2200 revs,when you drive off it hesitates and seems to hold back but then the turbo seems to boot in and it accelerates away until you change gear and then this happens again through all gears but this only happens for about 5 to 8 mins until the car is warmed up.The van will then drive spot on as though there isn't a problem.When on motorway can't fault at all drives like a dream.Have put in a set of injectors no change,had the head off and examined no faults,new glow plugs,replaced egr valve,numerous lenghts of boost hose,new edu at back of pump,had van plugged in on diagnostics nothing shown no engine management lights.Turbo seems to be working fine,can't think of anything else really so it's over to you,can someone shed some light on this it's driving me crazy !!!
Thanks in advance Marv.