Looking to change the plugs soon. Car runs on E85. Any power to be gained with coil packs? $605 is steep so I am curious if they're is any power gain there? Hopefully JPC chimes in they said they have a special plug they run in there NA car.
I am not a expert on E85m but can share some of my experience with some different plugs I have run
I have had the best luck with NGK LTR71X-11 part number 6510 ONE step colder. and projected tip
2nd Best luck Brisk RR14YS ONE step colder, projected tip
3rd best luck Brisk RR12YS TWO step colder, projected tip
worst luck Brisk RR12S Two step colder, NON Projected tip
Factory Plugs are a projected tip, so unless your only racing the car, with no street driving I recommend staying away from a NON projected tip plug. For a race only car that you will be changing plugs before each event they might be OK, but not for a daily driven car. They tend to foul quicker than a Projected tip plug
I won't say who installed a set of Brisk RR12S into my car, but they fouled so much that after a month the car wouldn't even start. They built and tuned the motor, so I took there word that was the plug, and heat range for my new motor. I then switched to the Projected tip RR12YS which didn't foul nearly as much, but were still a little to cold for my daily driven car. I have since switched tuners, who dyno'd, and street tuned my car, I am back to the NGK 6510's and the NGK plugs burn so much better.
I don't know what heat range you should use for E85 but these would be my recommendations
1 step colder NGK 6510 or if you want a silver electrode Brisk RR14YS
2 step colder Brisk RR12YS
All projected tips
I do have a set of RR12YS, I may use just when at the drag strip when I need a little colder plugs
Pics on some plugs, Non projected RR12S, and NGK 6510 I know different heat range, non projected, VS projected tip, and different tune, but will give you a idea about different tip designs
I think most people would recommend the OEM coil packs.
Tasca has them for $48.88 each, so thats $391.04 for eight, probably add $15 at most for shipping, and you are looking at around $405 for eight OEM coil packs shipped to you.