+1 on what Blind said. Sounds like you have gone through and did almost everything else you can do right now. I would put money that its a vacuum leak somewhere also.
List of all codes in case you didn't already have it
http://www.edgeproducts.com/product_...cle-pdf-41.pdf
P0301 --> Cylinder 1 Misfire Detected
P0302 --> Cylinder 2 Misfire Detected
P0304 --> Cylinder 4 Misfire Detected
P3000 --> Random/Multiple Cylinder Misfire Detected
P0000 --> Generic Ford Code for something is wrong
A few other questions that I would hae would be....How is the fuel pressure? What about the fuel pumps? Did you check the fuel filter?