More Power Spark Plugs?

Dear Ralph:
There have been many claims about replacing plugs on the Apex for a claimed 2-3 HP gain. One experienced rider even claims to FEEL the difference. Another rider claims the sled idles better, and starts faster. The magic plugs are NGK CR10EK, or CR10EX.
The experienced rider (well known Yamaha racer) said, “They have never fouled for me. They won’t do any damage to your engine. If you run the CR10EK on the trail for a while, and stop and put the stock plugs back in you will think you have something wrong with the engine, (slow response and sluggish). Put the CR10 EK back in and like magic the power comes back, it is that noticeable.”
So, what’s the verdict?
Carston Seales
Marion, Michigan

I asked Yamaha service about this, and they just laughed………….would any of you like to weigh in on this one?