So I am getting ready to change the plugs in my 7 and figured on using the same ones that came out of it. Bur9eq... all four are trailing plugs... why? And should i do the same?

 

Mazdatrix - Spark Plugs

 

stock leading plugs are "hotter" plugs than trailing, so a lot of people with higher than stock boost run the colder trailing plugs up there too to prevent the plug from holding too much heat and causing detonation.

 

Thanks for the link and the explanation. Ive always understood the reasoning on piston cars, just seeing a trailing plug in a leading spot confused me.

 

Something else to consider is that higher heat range plugs (BUR9EQ's in place of BUR7EQ's) will foul much easier if you're not living at redline. I had a NEW set of BUR9EQ's foul beyond saving in under 35 miles in my 20B in an untuned state. Not very fun having your car start, rev for a second then immediately fall on its face and stall...repeat 5 more times before it stays running.