A few days ago, I took out the K&N air filter that came with my X and put in a Motorcraft paper air filter. I didn't think to clean the MAF.

A couple of days ago, as I was driving, it started to hesitate and/or lurch while shifting into drive, and when going uphill dropping in and out of OD intermittently and not due to revs. I, of course decided to clean the MAF as that was the last thing I worked on. I didn't think to check for codes first, but after driving it and seeing that did the trick, I finally thought of checking for codes.. Sure enough, P0171 and 172 left and right bank System too lean.

So maybe the tip should be, when you're foolin around with the air filter, might as well clean the MAF? It could be confined to when switching filters I suppose. I didn't look at its maintenance cycle. Or maybe it doesn't get as dirty with the paper and no oil...

 

Glad you got rud of the K&N, my MAF was sandy after a clam digging trip to the Ocean. Back to OEM after that trip.