I might just return to the Bosch Plug, never had any issues with these.

It's not to say these Denso's are rubbish, it's when I'm on track giving it constant serious beans for 20-25min sessions, I just don't know if they are up for track work.

 

I just dont see how its happening to you but not any of us... and trust me there are guys going harder then you on these... with a lot more power.
something doesnt add up....
why would a plug hold up 1.5 or higher bars at 800 rwhp but not at 600 crank at lower boost?

 

If he is running with a weak spark on a stock plug gap, he would have more problems running with platinum versus copper. If his timing is different than you run, he will may increased combustion temperatures. His intake charge may also be higher than it should be.

OR........he may be running lean

OR........he just got a bad batch of plugs.

OR........his problem is unrelated to the plugs altogether.

 

Kevin at UMW recommends Bosch FR6 LDC plugs.