Searching around the web I can't seem to find a good solid answer to what plugs to be running. Some are saying NGK CR9EIX while NGK plug finder is saying to use a MAR10A-J. I'm guess both of those are OK, just one is Iridium and the other is not.

The plugs that came out of the bike are NGK CR9E. Nothing seems to be saying that is correct.

What spark plugs to use for a S4R Testastretta or S4RS?
Anyone, what is the right answer?

they went to mar10aj in the 1098, and it seems that the s4rs got them too, i guess build date early 2007.  all the pre 1098 testa motors ran champion (i forget the # now), but ngk equiv is cr9e.  i run the dual electrode cr9ek in them or iridiums.  not sure why they went 10, which in ngk is colder.

I've been running the same set of cr9eix since about sept 2006, ymmv.

CR9EIX   superb 

Looks like I will be running the CR9EIX.

Here is what I have found out while comparing all the plugs specs online. There are just some of the main differences.
Champion RG4HC       Standard Single Electrode          Solid Terminal
NGK MAR10A-J          Standard Dual Electrode            Solid Terminal
NGK CR9EIX              Iridium Single Electrode             Removable Terminal
NGK CR9E                 Standard Single Electrode          Threaded Terminal

My tech told me the CR9E is the equivalent to the Champion plug but lacks a cap or solid terminal so he recommended a different plug.