Still a slight arc at plug after changing them?

Are all the wires doing it? Then I would put new wires on it. If just one, I would swap it to another location. If the halo follows the wire,I would replace it. If the halo stays with the plug, pull it and check the gap. Large gaps require extra voltage to initiate the spark. The coil usually has the reserve. The wire sometimes not.The big fat square Accell SuperCoil seems to fire any typical gap. Mine has been firing the same Champions for 10 or more years.The original gap was .045. At 100,000 miles later, I have no idea what the gaps might be. Still starts click/vroom.Still hits 7200. Probably still goes 93/eighth
Only saints should have halos, and only in pictures.