Yes, as stated previously, a light coating of oil would be normal, plus breaking air filter housing mounts are a constant source of irratation the the owner of a m617 turbo engine. The mounting bracket also breaks off at the back. or the threaded holes become rounded out (with the latter you can use a nut/washer). I have seen air filters that are completely saturated in oil, especially on engines that are in poor shape (lots of blowby). Final note: it is not uncommon to have to repair at least the mounts on a yearly basis.