I've already done a number of searches and ready about some owners using the trailing plug in all four positions because they have a higher heat range (9) which holds up a little better for a modified setup. I got two extra trailing plugs so I'll have four new ones to put in but I wanted to hear from those of you who are already doing this just to make sure it will work. Thank you for the feed back, it's what the forum is all about.

 

Works great in my car, no problems. Lightly modded

 

Ahhh, the monthly "9s in all 4" post is a little late this month. Just do another search. You will find more than you can read in one sitting. I personally know more people that do this compared to those who don't.

 

Well, I did a lot of reading and sorry to be the month 9'er thread but thank you just the same!! Happy driving.

 

im using all same plugs, works great, no problems!

 

I switched to all 9s earlier this year. I've never noticed any cold idle roughness or any other of the supposed side effects. I haven't ran them long enough to see if they hold up better than the stock 7s, so we'll see if they go longer than 10k miles.

 

It works

 

Technically, the 9's are a lower heat range to reduce chances of detonation. If you are running stock boost, run stock heat ranges, If you are running over stock, run 9's all the way around. You could probably get away with running stock up to 12 psi with a good IC, but the disadvantages of 9's aren't that bad.

 

Never ran anything but 9s all around. No obvious disadvantages.

 

All 9's. No problem.

Cherry popped.

 

Mazda used the 7' plugs for emissions reasons.. Get rid of them and go with all 9's.

 

I have been running all 9's for many years. Motor is bone stock, but has reliabilty mods (radiator, downpipe, catback, ast, etc...)

Over 90K miles and she still passes emissions with ease every time.