OK,

I getr that either Bosch or NGK iridium plugs are preferred, but what part numbers to buy?!

When i use 2004 Crossfire vs. 2004 SLK320 I get Bosch P/N 9652 & 9600.
With NGK I am getting IFR5D10 & IFR6D10.

They are not even consistant, the two numbers are not always paired the same for the same vehicle on different parts programs!