If you are sprinting and you can feel your stem twisting, maybe you need a stiffer stem:
https://fairwheelbikes.com/c/reviews...g/stem-review/
Of the stems mentioned in that article, I've used:
- Thomson X4 (favorite)
- 3T ARX (favorite)
- Thomson X2
But if you don't feel your stem flex, then save your money. You probably don't need the stiffest around. Stiff enough is stiff enough.