Depending on how big and where the dents are will determine how much power you’ll lose. The closer they are to the cylinder, the bigger it has an effect on how the pipe makes the power. Pipe measurements are pretty precise so even a small dent can change how the pipe works. Even carbon build-up over time will effect how it works. We aren’t setup to fix pipes here at FMF.
Our main goal is to test, develop and produce exhaust products, and that’s what we do best here. There are many companies and dealers that can beat your pipe back into shape. Check in the back of any MX magazine for info.