I was browsin through ebay for parts for my 250sf and I came across an "open box" fmf power bomb header for my bike for $109 plus I had a coupon for 10% I had to use (expired the next day). It ended up being 100$ even (free shipping). I got the exhaust a few days later and it seemed like someone just opened the package looked at it and returned it it was still brand new (still had the fmf stickers and instructions as well) so I was happy about that. Now I just had to hope that the powerbomb header would bolt up to my Yoshi rs-2 slip on. After I removed the stock header I tried to put the fmf header onto the rs-2 and the fmf was too big of a diameter. Luckily I remember there being an extra new stock exhaust collar that was included with my bike when I bought it a year ago. I thought that must be it. I checked inside the stock header and indeed there was a collar in there. I put the new collar inside the fmf and then everything fit together like a glove. I also have a metal clamp around the connection between the two to make sure its a good seal (not sure if its stock).
So if anyone has the Yoshi rs-2 slip on and wants to get the fmf header, yes it will fit just make sure you have an extra exhaust collar handy (Kawasaki part # 11061-1055)

 

Nice pictures, tell me what difference did it make to the bike performance wise?

 

Well in my situation my jetting was a tad too rich. I think the addition of the header made the jetting perfect. I noticed a little better throttle response through the whole rpm range especially in the low rpms. Sound is about the same maybe a little quieter and deeper. Only downside is on my first ride after installing the header (to work) i burnt the bottom of my suit pants a little. I ordered the optional heat shield for 30$ that fmf makes for these headers and i would recommend anyone who buys this header to do the same.