Weird cold engine symptom

[silencer51]

For the last couple of days, I've noticed the following happen with my Meggie.

After the car has been parked for hours and the engine is cold, when I press start the engine comes to life immediately and idles normally however:

If I give it a little gas to rev it, the engine misfires (sometimes you can hear it, other times you can feel the engine vibrate as if a coil is misfiring).

This happens for 1-2 presses of the gas pedal, after that everything is perfect.

The car performs fine on the road, no flat spots, normal consumption, no weird noises...

I have had the dephaser pulley replaced about 6 months ago. I use Denso Iridium spark plugs and have had the throttle body cleaned thoroughly about a week ago. Also I have had the stock ignition coils replaced with Beru ones.

Could it simply be a case of bad gasoline? Or could it be the dephaser pulley is on its way out again? What should I do? No fault codes have been stored and as I said, apart from this the car works fine...

[silencer51]

Webcode? Anyone?