re: It already has an fmf on it but i think i am going to get the gnarly
This is your lucky day!! If it has an FmF on it, it already has a 'gnarly' 'cuz they are the same thing!
A short FmF primer:
The bikes you list are both 'H' models. FmF has changed their names over the years, but for the 'H' model they have two pipes, a rev profile and a torque profile. These are usually identified by a number stamped on one of the mounting tabs (location varies). A -30 indicates a rev, a -35 a torque. The rev pipe is a considerably larger circumference, about 14". The torque is around 11", both measured at the largest section of the cones.
When FmF went from 19 to 18 guage metal they chose the name Burly. Someone else already using that name took issue with it. FmF changed the name to Gnarly. That name by itself doesn't really mean anything. Saying, 'I have an FmF Gnarly pipe,' is saying you don't know WHAT you have. The term 'desert' refers to a rev profile, the term 'woods' to a torque. Both pipes effect the same rpm band of either the 200/220. That's not saying the pipes do the same thing on both bikes. Differences in carb size, port timing and static compression between the two kdx models have an effect.
Oh...some FmF pipes in the past have been mismarked on the tabs. Some have no marks at all. Some catalogs call the same FmF pipe one thing for the 200, the other for the 220. That's not helping any understanding of the matter.
Please go to CDave's JustKDX site. Please read it. Start on page 'one' and read everything he says. That will eliminate confusing statements as, 'It already has an fmf on it but i think i am going to get the gnarly.'
Have fun!