Miss firing?

Here I go again,

We have a 1996 C180 Auto Classic, as previously posted, it seems to have developed what seems like a miss fire, but I do not believe it is a miss fire as I have changed the plug leads and plugs and it appears to be sparking okay, it seems lumpy at tick over, and a little bit spluttery for the first couple of thousand revs, once past that it seems to run okay, on normal running you wouldn't think that there was a fault, but when it's idle it definately isn't smooth.

Anyone else got any ideas please.