I am debating which plugs to get for the 4.0 M60. I know the two stock ones are the Bosch F7LDCR or the NGK BKR6EK, but apparently the NGK BKR6EQUP from the 4.4 M62 engine can be used also. I have also heard the NGK Iridiums are very good but where do you get them? So which plugs should I get, should I stick with the stock ones or get NGK iridiums?