JAGUAR XJ8 TROUBLE CODE

Car Runs Great For About Eight Or Ten Miles Then Check Engine Light Comes On And When I Slow Down Or Stop Than Accelerate It Smokes Like A...

1999 Xj8 Running Rough Low Rpm Saying P0304 Which Side Is # 4 Cylinder On And Which Cyliner.

My Question Is What Do The Code Tell Me Is The Sensor Broke Or The Box I Can Drive But I Will Not Do So Till I Get An Answer. ...