Since the LSX coil on plug ignition is more powerful, what gap should I start out at, especially since I'm running the D585 truck coils. I don't plan on pushing more than 15psi.

 

My Camaro made 725 rwhp so far with stock gap and ls1 coils.

 

What plugs were you using? Heat range?

 

Is there any reason not to use an iridium plug on a turbo setup?

 

I used stock heat range and I tried both- Ngk iridium and acdelco platinum 41-943. Iridium plugs last forever.I've read somewhere that the reason is iridium or platinum are not recommend because in case of detention accrue it could break the tip of copper plugs and the detention will stop, but with iridium plugs because its stronger metal it will not break off and detention will continue to happen and cause engine damage.
I had two supercharged motors so far and I used iridium plugs with no problems so far.

If you do some search you find that most people with force induction application gap there plugs between 0.24" and 0.35".

Vortech recommend starting point of 0.44"

 

There's no reason not to use an iridium plug that I can think of. Only thing is the harder tips are rather brittle so if you were to try to adjust the gaps you're quite likely to break one (or more). Considering most FI motors are run rich with frequent plug changes I always run the cheaper NGK TR6 plugs at around .03 to .034 with my LTCC.