torque vs. rev pipes
for what it's worth.
i ride with a number of fellows with kdx's (mostly woods riding in the great pacific northwest). some ride 200's, & some (including me) ride 220's. all with stock carbs. all with different pipe configurations. i run an fmf gnarly rev, with a turbine core silencer. it's power characteristics are virtually identical to my buddy's 200 with a torque pipe and same silencer. go figure. i have another buddy with a 220, who's running a stock pipe and turbine core silencer. that appears to be the best of the bunch. it's retained it's stonking low end, and added considerable top end. it won't rev quite with mine..., but the difference is negligable and pretty much moot for woods riding.
can't comment on the "other guys" pipes. i've always run fmf's because of their reputation for working without unduly sacrificing some part of the power.
have fun!