Judge,

Which iridiums are in the car now? what brand, what heat range what gap?

for 10 psi on stock turbo i would reccomend NGK BKR6EIX (call # 6418 ). gapped to .030"

anything else and you are asking for trouble!! also, Denso plugs are crap never run them. lastly, if that doesnt solve your problem you might still have a coilpack issue