My SVT was stumbling very badly so I switched out my Ford Racing wires for the old set that was on the car. It is driving so much better now. I had less than 20k on them and the old wires had over 60k. I have been feeling the stumbling for some time but it got much worse recently. I just couldn't believe it was those wires. I guess I will go buy some new ones since there is still a little bit of stumbling. The funny thing is my wife�s car has the Ford Racing wires with more than 30k and no problems. So I guess it really is hit or miss.
