I'm always amazed at these " Bosch Platinum plug threads" and the "anti-Bosch" bashers, I usually run nothing but Bosch Platinum/iridium, I have them in everything from 318's, 340 6 pack, 440, 440 6 pack even my V10 with ZERO issues, plenty of miles/years of usage.... I don't see any of the supposed issues that the same posters have that always condemn these plugs?....I actual dislike AC, Champion plugs (pure crap) NGK is a 2nd choice if Bosch are not in stock or available, as far as the OP's question of replacing Bosch Platinums? I've never experienced a bad Bosch plug(s) over the decades, I'll generally change them out around 75-90K or 3-4 yrs on a DD just for the hell of it...
Mike
My experience has not been as vast as yours, but I have used them several places, and never had an issue. In my old carb'd 2.2L engines, they were the trick to curing a random miss when idling in open loop.
