you can use either.
The biggest issue is with re-oiling it (K&N oil is fine). However, less is more and make sure you let it sit on newspaper for a day or two to soak up all the excess oil and then some. Otherwise, you'll eff-up your MAF. Then costs saved from not buying a new air filter will be quickly evaporated by spending 3-4x on a new MAF... You can usually find BMC air filters on ebay pretty cheap FWIW.
