There are a half dozen TTR125's where we ride, we own 2. Dropping an after market pipe on with the aforementioned rejetting and airbox mod does make a pretty big difference. We have a PC T-4 pipe on one bike and an FMF on the other. We ride with folks that have the thrust chamber and the TTR pipe. All of the pipes seem to have similar performance gains. The FMF is a little stronger on the bottom and the PC is a little stronger in the mid and top. The only drawback is the sound level. The FMF is louder than stock, the PC is next loudest, both are tolerable, the BBR in our group is much louder than the other two. Check the prices too, there is a significant difference.