I tested the FMF Gold Series SST pipe on a 2003 Yamaha yz125 and it is a great pipe for riders who want smoother power.
The power-band got a healthy increase of horsepower and was broadened; resulting in less of a 'hit'.
The bottom-end power was close to the same as stock with the SST, and the mid-range was slightly better than stock.
This FMF pipe makes the bike easier to ride because it's not as snappy, and the throttle response was spot on and hit right off of idle.
The FMF SST pipe also gave my bike a lot more over-rev compared to stock.
That was probably the biggest change I felt because the power just dropped at really high RPM with the stock pipe, but the FMF SST pipe kept the bike pulling for much longer.
I really liked that because I ride in the high RPM range.
Overall it's a really good horsepower addition and makes it easier to ride if you stay in the mid-range and and top-end because that's where there is more power, plus the over-rev adds additional gains that can greatly help faster riders.
But for beginners or riders who like to lug the bike around more, it's better to stay with a stock pipe or an FMF Fatty.
The FMF SST is made of high-quality Steel which is stronger and more durable than the stock exhaust pipe.
The SST is also chrome plated, which gives it a great shiny look that lasts long.
Thanks for reading this, and I will have more reviews to come!