You do not NEED colder plugs w/ spray. Everything you get w/ a NOS kit is for "safety" so they do not get sued out the yin for fuckin up peoples cars. It is a SUGGESTION. Like they suggest 3 - 4 deg retard... I am -2, standard NGK plugs, BIGGER jetting than the kit requires and yet I am not hurting the motor or the kit. Fuel psi safety switch has still never stopped my fun yet. But yes, it is highly suggested to get 1 heat range colder when adding the spray.