Renault Laguna 2 1.6 'stutter'?

I have a 52 plate Laguna 1.6ltr which has developed a 'stutter' between 2600 rpm and 3000 rpm.
The problem is only apparent under gentle acceleration and clears when car is driven hard.
It has done 87K miles and has full service history.
The fault is similar to a misfire but engine runs great out side of this rev range,Any ideas greatly appreciated!