Running rough

[Webb]

Hi guys I'm new on here . Having trouble with my wifes a3. It runs fine at idle but as soon as you take it off idle it vibrates very hard like it's going off a cylinder . I have just fitted a new clutch and flywheel . No different . So I sent the injectors off to someone at Leeds.  They said they all needed doing 720 quid to recon them . Got them back and all worked perfect for 300 miles . Now it's the same as it was before . Also fitted inj loom  while I was in there . Any help much appreciated 

[WPAWS]

Outside my field of expertise but i`m sure someone here will pop along shortly and offer some advice