naah, its actually a piece of stainless mesh.. u buy a whole roll, very poppular here, although a sieve is a good idea... well never had any probs *touch wood* sure a bit of dust gets in but thats what ur oil filter is there for lol..
i change my oil every 2000kms so not really a problem
also i dont drive the car in the rain since positioning the turbo where it is.. iv had mesh on my car on 9 different turbos to date in the past 4 years.. none of them ever went bad
i do plan on makin a kinky airbox though soon
but thats another story