my 92 SC400 need to replace spark plugs due to 100000 miles tune up. I was thinking bout putting E3 spark plugs. Anyone would tell me what specific E3 plug i need? do i need a new wiring harness or anything else? Any advice to do so?

 

I am not convinced e3 is worth the extra money. I have yet to see side-by-side comparison between a normal, brand new plug, and an e3 plug (every dyno test I have seen, and they're all from e3, implies old, worn plugs as a comparison....derp...).
Unless somebody can prove that wrong, I recommend sticking with NGK.