I read somewhere on this forum that the Bosch +2 platinum plugs were not a particularly good spark plug, designed for longevity and not for performance, and that copper core plugs are actually better performers.

So I tried a set of Champion copper core spark plugs and that cured the problem! So much for the bonehead mechanic that charged me $170 to simply read the code off of the computer and suggest replacing all of the coils for $1700.

There was some perverse joy in throwing out $6 spark plugs and replacing them with $1.19 spark plugs that really work.

I will never buy Bosch spark plugs again.