i have the yoshi slip on it it fits perfect on the stock head pipe no air leaks at all check my page it has a pic of the pipe on my yfz

 

got a full yosh pipe on my yfz450, i niticed a big power differance more in the bottom end my kit included the header, slip-on, jet kit, and a k&n airfilter, with outerwear filter aswell. i put the mods on and was amazed at the incress in power, after i played with it a while i took the spark aresster out...it ran alittle better...and another cool thing bout that, made it sound alot better, and if ur track has lights...looks wicked at night with a big blue flame comin out ...lol...the price to do it..$950...the look on peoples face when ya scare the poop out of em'...priceless!...good luck

 

I agree with YFZwillie about it running better with the spark arrestor out i run a full Fat Boy 4 pipe and a bunch other mods in my signature and people think it cool when im racing at night cuze i hit the reev limiter every time[img]i/expressions/face-icon-small-wink.gif[/img] if u go with the full yosh head pipe u will be glad u did down the road pluse if u do more after market things and go all out with the motor it will pay off

 

there was a guy at little sahara OK, that had and echo tip for a muffler and he was by no means slow