Took my car into the mechanics today for a standard major service and when i got it back it was idling very rough and lumpy sounding. They have looked at it and have no idea what is happening but there is also a 'knocking' sound as you come off accelartion now. Sounds awful but is running fine apart from this.

Any suggestions as to what is going on? the car is a MK1 with a '91 16 valve 2.0L conversion.

Cheers