2002 Volkswagen Golf Intermittent engine misfire

Management line on permanently, and flashing when engine misfires and loses power.
Coil pack, leads and plugs changed but light still on and fault still their.
Don't want to go back to garage without some idea of what else to do.
Had same problem 2 years ago, new coil pack sorted misfire but management light stayed on. Mechanic said as not a VW part, might mean light stayed on?