Tonight I took advantage of the good weather and cleaned out my twintake filters, washed them and left them to dry in the sun. Going back under the bonnet, I noticed that the upper/front-facing filter housing has been rubbing against the engine coolant return hose
(ignore the silver duct tape, that was to try and stop the spring clip from wearing through the twintake silicon pipe)
Luckily it hadn't yet worn right through, but this has happened on mine after around 18 months of use.. you can imagine the inconvenience of this hose springing a leak!
Get it checked people