Thinking a new air filter might be due as I don't know how long its been on the engine but looking at the regs the filter is a K&N 57-0044 but everywhere I seem to look it says this has been superseded by K&N 57-0176,help and advice required please,might even treat it to a new set of plugs
The answer per the K&N site is to use filter part number RC 9250. As you say 57-0044 is out of production not to return and -0176 is the entire kit. You only need the filter and the above is the part no for that.
Alternatively give the one you have a good wash in Fairy liquid and let it dry naturally .... save £54 plus postage ...
Jamie is quite correct on the part number info - must change the regs as I keep forgetting :-(
Another good way of cleaning your existing filter is a good blast with an air line from the inside out.
Thanks Pete,thought about the airline route but looking at the filter it looks pretty crappy,new one sourced on fleabay from YB Filters,£39.50 free postage so one is on its way,ironically when I checked where its coming from its just around the corner from where I work