2017 Camaro ZL1, cam, headers, port heads, Whipple 2.9, VP109, Alky Control, 19 psi, Denso 5341, ITV24 plug, with competent tuner and very conservative timing. On cylinders 1 and 6 has taken the ground strap once and now the porcelain for a total of three plugs each time. AFR is good. Any ideas? Has always been those two cylinders other look fine. Lean injector??