There are only two things I can think of that she might have heard about. First, if you over-oil your K&N when you clean it some of that oil can get on the MAF sensor, and your engine will run a little rough. It's easy to fix with a (at most) $5 can of MAF cleaner. Second, you'll be getting more air into the engine and the air will flow past the MAF differently, so that can cause you to run very slightly richer or leaner, but not in any way unsafe. I've never heard of any issues that MAF cleaner won't fix and most guys see a little better fuel economy. Also, the computer will adjust the fueling over time.
