Hi,
I've just ordered a set of NGK plugs from ebay for the bargain price of 32.38. They are listed as being for a C55 AMG (so there are 16) but I believe they are the ones for the NA 3.2

link:

NGK SP PLUGS x 16 MERC BENZ C55 AMG 5.4 02/04- IFR6D10 on eBay (end time 10-Feb-10 05:59:18 GMT)


Just thought I'd share....

Steve