I emailed BRISK about what plug to use on a mildly modded 3.8l s/c V6 with about 11PSI, and got this response today:
Hi Lee,
the spark plug you need is Brisk Silver Racing G14YS. That is a spark plug specially designed for forced induction applications, nitrous or methanol injection.... and we have many vehicles with over 3500Hp running the Brisk Silver Racing plugs and setting world records. The LGS is excellent choice for N/A and stock boost forced induction applications. Your vehicle have powerfull ignition system and will handle the GOR14LGS plug at your boost level, but due to the higher boost and altered A/F ratio the lifespan of the plug will be relatively short.
Hope this info will help.
Best regards,
Chris