Yeah, either a vacuum hose or it's the MAF, the stealer is jerking you around. The K&N is notorious for fouling up the MAF with the oil. You can clean the MAF yourself. Just unbolt the MAF and spray with some electrical contact cleaner. Make sure the cleaner is "plastic safe". You can get a can from any hardware store or Radio Smack.
Like I said, take off the MAF
carefully and librally spray down the little thin wire(s) in the MAF. DO NOT touch the wire(s) with anything but the cleaner, becuase if you break it, it will cost you 3 Benjamins for a new one. Here's a link for the procedure in detail, it's about half way down the page.
http://www.4x4wire.com/toyota/mainte...ncep5.html#maf