Definitely get rid of those yfz shocks. I would not call it a mx build with those on it, they are far too stiff and will cause huge arm pump after a few laps.
The yfz shocks are longer and might have more sag making it more difficult to lift the front end, your rear shock might also be soft and soaking up some of the power.
It is a strong possibility that you have excess caster, and this may be the reason it feels unstable at high speeds, it’s a trade off, low speed agility vs high speed stability. Do your upper a arms have spacers on one side?
If you plan on hitting jumps and whoops you should really look for a shock with high speed compression adjustment, but the float 3’s should be a big improvement over standard yfz shocks
-Ben