I had a similar problem. My local Ford dealer diagnosed a dirty MAF sensor which they cleaned (fixed the poor fuel economy, not running rich) and they also cleaned the IAC to level off the idle. My idle still jumps when I shift from any gear into park or neutral, the Ford tech. said that was normal on these cars("they tend to spike")
Have look at your plugs, they will tell you how well your engine is running. Mine were black (rich) before the above fixes were done!
Good luck.
The Ford tech also suggested I get rid of the K&N!~ I did, and replaced it with K&N conical fiter!
