I have a PA28-151 warrior with Slick Mags (4370 & 4371). Yesterday while changing the oil and filter I noticed that the P leads on both mags were cracked and should be replaced. The set up for the question is both P leads are a single wire that is not shielded. There is not a separate wire that is shielded. I have not yet looked under the IP to see if there is a ground bus bar in use for the switch. I understand that the shielding is for reducing radio noise. The various posts that I have run across has me perplexed as neither Piper or Lycoming seem to address the issue. QUESTION: If I run a shielded cable from the mag to the switch do I leave the shielded cable un attached at the switch end? If the switch has or has not a terminal that is grounded.