When I put my 2 bros on this spring it was a noticable difference. I've since added the P3 tip to quiet it down, didn't seem to lose much of the power gain. The 13t sprocket then helped alot as well. Now to rejet, which I'm hoping will get me to where I want to be.

 

Hey guys,

Whats the part number on the FMF Q4? I assume its just a slip on?

 

i would like to add that im runnin my 07 with no mods with the exception of my two bros slip on and i rejetted the bike that i can wheelie 1 and 2nd fairly easily without use of the clutch

 

I went to my local dealer for the Q4 slip-on for my '07 KLX250S. They looked up the part number for me, I don't remember what it was. Anyway, I asked for a discount since I bought my bike there. With tax, it was something like $301.; cheaper than any place in the Internet. Doesn't hurt to ask.

 

I seriously doubt that. You can't extract all of the power potential by just by drilling out the baffles. 1/2" won't get it ...in this case a bigger hole is a good thing.