>"I have a Powercore 4 pipe on my bike. "
I have installed the Powercore noise-reduction spark arrestor on a WR250R, it quiets down pretty nicely.
About $34 bucks I think.
(Note: This was installed in a Q4 pipe, had to bend the spark arrestor screen to get it to go in.)
"I don't really know, I've been too busy falling down."