were designed using standard copper Bosche Supers and therefore NGK are acceptable alteratives for L-Jectronic based engines so your 1/2 right, the sensitivity of the Motronic sys. is made to run at the heat range/sustaince of the Silbers(silver) and from what I've read on the Big Coupe Group's page, a noticable difference in idle quality from the silbers compared to any other including Platniums.