my son has the yosh system we like it really well. it came with the t.e.c. insert which is basically the quite core insert with spark aresstor. with the quite core it sounded decent but with the quite core out it sounds awsome.
I have an 04 kfx 400 i use an fmf hi flo head pipe with a LEXX slip on with mid pipe plenty of power plenty of growl plus optional tip so it can be legal on db best of all you can buy the two for a reasonable price low price =more race fuel a win win !!!!