I have a 2002 325xi with 160k and am getting a P1351 code. A misfire in cylinder #5. I only get this code when I step on the gas hard, I then reset it and it drives fine until I hammer the gas and then the code comes up again. I changed all 6 spark plugs, and the #5 coil pack and the same thing happens. I rotated the coil packs and it still comes up with cylinder #5 misfiring code. Does anyone have any ideas on what could be wrong?