is there a way to change brake bias in my kia to reduce nosedives under hard braking?

 

Changing the brake bias will not help nosedive. Short of installing and aftermarket brake pressure adjuster, there is no way to adjust brake bias in 99% of street cars. Adjusting brake bias is a difficult and tricky thing. If you get it wrong, your rear wheels will lockup too easily. Even if get it set so that all 4 wheels lockup at the same time on dry pavment, on wet or slippery surfaces, the rears will lock up MUCH sooner.

Stiffer springs will help the nose dive problem you are having. They are also much safer than trying to mess with the brakes.