FMF Exhaust for 02 YZ250F

Hey everyone, I bought this FMF exhaust a couple years ago for my 02 YZ250F at the Chaparral Sale. It was marked for my bike, but I am doubting it's compatibility. The header seems very small (small diameter), it is even smaller than the stock header. When installed, it fits fine, but the bike runs horribly. I know I probably need to re jet, but don't want to if this header isn't correct for my bike. Anyone know what I should do? If this is not correct, could I just buy the correct power or mega bomb header and use this muffler? I am new to exhaust systems.

Ideally, I would like to keep the stock jetting because usually the bike runs smoother stock, but usually can't when redoing the whole exhaust. If I just get a slip on muffler, will I still get an increase in power?

I just want to improve my bikes power without messing with the stock running smoothness and reliability. Any advice will be GREATLY appreciated!




 

Alright, well, I got in touch with FMF and sent them pics. They said it was a typical Hi-Flo system and it would work for my bike. I just need to re-jet the main jet. Is that really all I have to do to make it run correctly with this exhaust? I want it to run smoothly. Will this kick up my power?  

FMF are usually real good at telling what jets you need with there exhaust. I would try what they say and see how it goes.  
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I love this dirt stuff.