other options which is much cheaper is the Kenne Bell "boost a spark". It works the same as the old XS engineering Power pack. From what I can tell by the wiring and by the setup.

I have/had the XS power pack on for nearly 4 years and it works great!!. Just wish they would come out with the version 3 soon. But that's another story.

 

In my EFI University class, my instructor warned us against using Iridium tipped plugs in high power applications. Yes, they are nice in the fact that they last so long. HOWEVER...since the tips are so tiny, it's much more prone to heat buildup and causing pre-ignition. Copper is a great conudctor of heat, therefore much of the heat put in from the combustion chamber is wicked away quickly. Out of all the 600-700HP+ Supra guys I've asked so far, all of them run the NGK copper plugs.

How long they last is usually not an issue because for most of those guys their cars are weekend warriors. They would be lucky to put more than 2-3k miles a year. On lower boost applications, yes the iridium plugs work fine and last longer. Just be careful if you want to use it on a high power/boost setup.