OK.  So the NGK's that BPD uses and/or the Denso's that Crash, Darreli and FirstSHO use MAY be a step cooler than the stock Motorcraft.  But as far as I know, the 534's and the 528's from Motorcraft are the same temperature.  I'm fine with my 534's even though I don't think they are a step cooler.  They are approved for my tune, they are gapped at the right gap and they are a step up in material from the 528. 

I ran brisk plugs in the viper truck and they were fine.
If you go to their website they sell their plugs for turbo'd applications.
Www.briskusa.com they make only performace plugs.

The sp528 and sp534s according to a few online stores show them both to be an Iridium plug. I do think.however the sp 528s we're replaced with the 534s due to random misfired that were occurring with the 528s

It's unbelieveable.  I just googled the sp534 and sp528 again.  Between PEP Boys, Jegs, ORielly, Autozone, Amazon and Ebay, no one agrees on whether either are platinum or iridium.  I default to the SP534 being the latest and greatest. 

I have to agree the sp534 are the latest and greatest.