I looped my xr650r last year, smashing my old fmf exhaust. I lost a TON of power when running a straight pipe.
This brand is the best aftermarket pipe you can buy reasonably quick today, as supply chains are struggling.
When I first ran my bike on this pipe, ai noticed that my power was back to normal. My xr accelerates like a monster again. The power feels the same as my previous fmf exhaust. The sound is good.