The 6R12pp plugs are setting off the check engine light and giving me a code p1353 no front cylinder combustion.Went back to the 6R12 standard plug and engine light stays off and it seems the problem is solved. Anybody else ever have this probelm? H.D. shop told me these 6R12pp are the plugs alot of people are usiing.I guess I wont be.I guess Ill use the cheap ones......