Wynns Carb Cleaner, it's the dogs danglies, Stu on here was having major problems with his, we sprayed a load of carb cleaner through it, worked perfectly afterwards, the power of the spray is enough to clean the elements, and it evaporates afterwards leaving it spotless. Halfrauds do it for about 4 quid a tin, not much else you can do to clean it really.
EDIT: Sorry meant to say obviously take the MAF off first so the small hole that leads to the elements is exposed and spray directly into there.