I'm having my car worked on and the tuner mentioned that he had heard that you should run colder plugs on either trailing or lead and regular plugs on the other.
Has anyone heard of this?

 

what, no. it depends on what engione you have and what year engine it is. there is a difference on 86-95 13B's and th 79-85 7's use the same plug for leading and trailing.

 

Yah, what the guy above said. You normally use BUR7EQ's for leading and 9EQ's for trailing.

 

I talked to the guys at Mazda racing and also racing beat and they said there would be no purpose for running the spark plugs like that. Does any one have a reason for running the plugs like that?
Thanks

 

Like what? Hot in leading and cold in trailing? Because the manufacturer recommended it for stock cars, that's why. People run different plugs on modified cars because they are running higher temps so if they didn't change them they would fry the plugs and maybe even chunk them into their engine. The application determines which plugs you should use. Some people even run EGV's which are motorcycle plugs.