I know a lot of people might scoff at this, but I have an fmf and I think it works pretty damn good.  I got it because I didn't want to drop $800 at the time for a Shearer, and I'm impressed.  I don't have a  lot done to my engine, just the pipe and a RAD valve.  Otherwise everything else is stock.  For a 250 the LT hauls the mail, and I have modded Tecates, a Tri-Z, and 250R to compare it to.  I guess it is a testament to how good the LT engine it--it's an underrated machine.  I'm not saying the fmf is the best pipe out there, I'm just saying it is more of a performer than I expected.  Pretty good results for $300.