what spark plugs should i use with my new sz49 set up my 04 sti??

I just went to the one step colder NGK iridiums on my car and I am still on stock turbo. Car is much smoother now and it helped to clear up a misfire issue that I was having. I got mine from sparkplugs.com and paid a little less than $50 with 2 day shipping. Stock plugs were starting to get a white "soot" on them which is a classic sign of too hot a plug so I bet you really need the one step colder with that much turbo.

Good Luck