Vibration

Hello all.

Ok so I've got a 2014 2.0ltr Superb which had a new egr cooler fitted by the dealer back a few months ago under warranty.

Since then I've had a vibration which is intermittent.

I've had all four injectors tested and they are operating correctly. Though plugging vcds in and the figures for two are out slightly.

I was sat idling the other day and the engine went from fairly smooth to rough like a switch had been flicked. Since then I've discovered that if I thrash it, the engine smooths out. Otherwise it's quite rough.

I was beginning to think it could be the DMF.

Has anyone else experienced this and does anyone know if the EGR could cause this?

Thanks.