The problem is that this motor has tight tolerances. When you keep on the gas that long the blower starts to generate so much heat that the pistons melt. Usually 7 and 8. The head cooling mod does not prevent this from happening, but it is a precaution that people think will help because it cools thoe two cylinders off. It's just not cooling it enough to where that WOT pull won't affect it.
Long story short, don't do it. Too much heat builds up. 2nd-6th gear pull at WOT is insane. Don't blow your motor or kill yourself/others.