Bongo Fury

I thought id have a look at the air filter and discovered it quite dirty with an oily dirty texture on one side - is this a tell tale sign for a faulty development or shall i just change and c - it wasnt much about the size of 2 inches round

Depends how old the filter is. Air filters on diesel engines get dirtier quicker than their petrol counterparts. I tend to rotate the filter 180 degrees after 6 months and replace it after 12 months.

That Itchy & Scratchy avatar was getting annoying. Hope this Bernese puppy is less irritating

I have the same size oily mark on my filter

the oily marks are nothing to worry about,just the product of a hard working engine,a good clean up should do the trick,thats all i do to mine paul.