a4 2.4 v6 miss fire when warm

[scanny1]

i have a a4 2.4 v6 audi 2002 which has developed a miss fire it happens when the engine is hot,ive replaced spark plugs ,ht leads ,coils .and its still the same .but for a while before i had the engine management light come on a few times saying catalyst below threshold.would the cats cause this to happen if they have gone

 

[scanny1]

any ideas ??

 

[marktdisport]

Could it be a sticking valve ??

 

[Greeny233]

Could be a lambda sensor fault.