One thing you can do is to try to isolate exactly where the wobble is coming from. The best way is to have someone else wobble the stem while you place both hands around the stem in various places: where the stem goes into the anodized red ring, where it meets the clamp, the base of the clamp then a little lower where the suspension approaches the bottom of the gooseneck (frame). There is also a bolt pointing upward into the stem from the direction of the tire (often with little grub screws coming in from the sides locking it into place).
If you can isolate where the bulk of the stem flex is coming from, then you can probably reduce it.
One thing that will help is just riding experience. As you get more used to the power, you’ll get used to shifting your weight around more by using your legs, and rely less on the handlebars. This actually makes a huge difference.
-Paul from ESG