Which Spark Plug?? K24a4 Honda Insight "eco build"
 

Long story short I've abandoned the turbo 2.0 idea of eco and power as after 1 year I was boosting more than not and averaging 37 mpgs (and smoking most on freeway)

I now have a bone stock K24a4 with the Accord 1-5 gearset and a brand new 3.4:1 FD. Will also have Kpro and will be maxing out the leanburn capabilities.

First question is spark plugs, OEM 04 Accord? Hotter?

Next is just any general tips or tricks one can give on a fully programmable K24a4, 87 octane, OEM Accord header and 2" free flow exhaust.

I can't contribute any knowledge to this conversation, but I'm curious to know why you think hotter is better? Is it that lean burn is cooler and knock is not as likely?

I have zero experience tuning for economy and not a lot tuning for power but generally for boosted cars with high cylinder pressures colder plugs are the norm. My car weight half that of an accord as well as better aero so much less engine load, that my only rationale on the hotter plug not so much the lean burn, I just know I will be experimenting with it.

Rule of thumb used to be that colder plugs were better suited to higher-octane fuels, boost and higher compression ratio. Since you plan to use 87-octane gas, going with hotter ones may fare well.