I want to know whats the best spark plug to buy and which heat range for my ep91 n/a i have a few mods, glanza inlet mani, corolla exhaust mani, and coming in a few days 200 cell cat with a straight through cat back system 2.5" with 4" back box also have new plug leads fitted and will be replacing dizzy cap and rotory arm, whats the heat range that n/a run on? am i right in thinking its 6heat range i am looking for? raffa