1998 A4 1.8t ADR engine

[kit]

Hi, My wifes says her A4, when she starts up, runs a bit rough and the rev counter drops as if its going to stall so she gives it some gas for a minute and its fine. She says its normally when the engine is cold but has on occasion done it when shes been shopping and come back to the car after an hour or so.

Also while I was stood at the drivers door when she started up there was a strong smell of fuel but i looked round and couldn't see any leaks

BTW MAF replaced 2 months ago

Thanks in advance