Expedition running rough

I own a 1997 expedition 5.4L.It runs extremely rough when I accelerate and it seems to do it when I am above 45 MPH and around 2000RPM or above.My check engine light came on and was blinking.When I put it in park and rev up the motor it seems to run smooth.Anybody have any answers to my problem.I just recently read the computer code and it came up as P301.

The P0301 code indicates that number 1 cylinder is misfiring. Time for a tune up.