check engine light hell

2002, had codes 0304 & 0401 cleaned egr ports replaced spark plugs and wires, changed coil under wiswinds advice (thank you). Car ran lots better imediately, but started to chug and idle wierd while stopped in gear. I put the code reader on it and im getting p0304 still and now getting 0171 & 0174 too lean bank 1 & 2. help please.

Have you had the upper intake manifold "isolator bolt" TSB performed?
http://redirectingat.com/?id=252X400&url=http%3A%2F%2Fleckemby.net%2Fwindstar%2Fwindsta r01.html

The other thing that comes to mind is to hunt around for a vaccum leak....maybe a bumped hose....also verify the PCV line from the front valve cover (for 1999 and newer) to the upper intake manifold.

I most likely already mentioned using a can or so of Berryman's B-12 Chemtool in the gasoline tank to clean up the fuel injectors......as I have gotten misfire codes along with lean codes from dirty fuel injectors on my '96 3.8L
The may have improved the spray end of the injectors in later years as it does not seem to be as common on newer windstars.
However, it is worth a try.

you can fix teh 171/174 codes easily. follow the sticky post at the top. that should help with some of the idle issues.