When to switch to colder plugs

[Seattle GST]

I have posted all mods to date in my profile, and I have been running NGK's one band colder than OEM. I have had runner number 3 foul 2 plugs in the last year, and while getting a new Master Cylinder the Mitsu tech informed me that the OEM plugs would be better both in performance and apparently he told me that the colder plug does not fit properly? I am baffled by his last statement as I compared a 7 and 6 while at home and by my viewing, they look identicle in size/fit.

Should I switch back to OEM temp, or should I continue to run the colder plug.

I do get a single backfire when easing off the gas in 3rd gear. It happens on the same downhill sweeping right that I take every morning, if i keep on the go fast pedal it will not backfire, but if i lay off (to be within the speed laws in that area) then i backfire.

 

[L2RTSiAWD]

You don't need one range colder.

 

[Sic95gst]

I don't have a lot of mods done and i'm running the 7's and it has only made my car run ten times better, no fouling and no backfires. mine fit perfect!

 

[midnght]

You will be good with the stock heat range plugs.

When you get rid of that T-25 you will probly want to go one range colder.

 

[Defiant]

the Mitsu tech informed me that the OEM plugs would be better both in performance and apparently he told me that the colder plug does not fit properly?

And some wonder why we call them Satan.

Stay with 6's until you get over 250fwhp.

 

[theycallmebruce]

are there bad effects to running colder plugs in terms of performance?
i know they will foul faster due to not enough heat to burn off the carbon.
i'm running colder plugs and wondering if i should switch back to the 6s.

 

[UrMyStlkAl]

I'm running 7's also and don't even have an exhaust, I'm mostly stock. Wonder if there would be any difference in switching to the 6's.