Since the lead is a shielded wire I would caution against it.
Here is what Aeroelectric connection says about the P-lead.
"Note that I show shielded wire between the
magnetos and the magneto switches. Spark plug wires and
magneto p-lead wires are the ONLY wires in the airplane
which are ALWAYS shielded. Further, p-lead shields should
be grounded to the airframe/engine only at the engine end. The
shield is used to provide a ground for the "GRD" terminals at
the switch but no other connection to the shields should be
made at the instrument panel end.
Noise sources, noise victims and noise propagation control is a
large topic for another time. For now, understand that shielded
wire has limited capability and reduces or eliminates only two
of three common noise propagation modes in vehicular power
systems. Shielding of most other wires in an airplane, unless
specifically recommended by equipment manufacturers, is
unnecessary"