Spark Plug Heat Range

[XfireZ51]

I did a scan of a standing start going thru 3 gears last week. I got Knock retard at top of third gear. So now I’m wondering if that was happening at track at BG. I pulled plugs to see if there were signs of pre-ignition or was it false knock. There were some tiny specks on porcelain but sooty not metallic, and right at the edge of porcelain as it goes horizontal towards center electrode. Also, looking at the ground strap, it changed color at the weld suggesting heat range was hot. Base ring color was black telling me WOT fuel could be leaned out.Plugs were barely torqued so I took care of that. I may do another scan and see if I get same results. If I do, I may go to a slightly colder plug. Right now using AC 41-630 having replaced the NGK Irdiums TR5IX (Came with car, so no idea how long they'd been there) that were there.
Anyone want to chime in on which plugs and heat range they're using?

Here's a very interesting quote from this article

http://www.articlealley.com/article_467790_31.html

"...When an engine is modified for high performance and its power is increased, the stock spark plugs very often result hottest than necessary due to the new power reached at higher RPM and the gasoline would end up pre-igniting or detonating without the need of an electric spark, creating an uncontrolled explosion that would severely damage the engine.

Be aware that never! Never a high performance modified engine, can continue using the stock spark plug, because more power is more energy, and more energy always is more heat.

Unfortunately, even very experienced mechanics have difficulty in detecting the differences in these situations that are very often misunderstood, misleading them to search the origin of the troubles that the spark plugs are showing, in the supposedly wrong air/fuel mixture, cooling systems troubles or other mechanical failures.

It is absolutely clear that is doing lack more information about the true one and transcendental importance of the heat range of the sparkplugs. This exact selection is critical!

Only with the proper Heat Range will spark plugs sustain the perfect combustion process that keeps your engine's top efficiency and functional reliability.

But only a few of the most selected and experienced engine tuners know how to select the spark plug with the proper heat range best suited to match these different conditions, or the specific engine's level of modification, but them reach it only after long hours of expensive and difficult testing by trial and error with different spark plugs sets of different heat ranges.

What you need to find is the spark plug with the heat range, best suited to the combination of your own specific, individual and particular driving habits, traffic, weather, and engine operating conditions, fuel quality, that can be affecting your engine performance; tailoring this selection exactly for you driving habits or life style.

This is the only way that guarantees to achieve the peak power, performance, endurance, better mileage and the lowest emissions."