Update is available. In the API there is no such thing like a diffuse level parameter as much as I can see, not sure how it is done in 3dsmax.
Diffuse level is a multiplier for multiplying the RGB of the diffuse color. In my Blender exporter, I just had to expose the parameters to the user and calculate everything myself on the back end. I can't imagine it's in the API. There is also a translucency multiplier. The formula for it is:
diffuseMultiplier *= (1.f - translucencyMultiplier);
Then you multiply the diffuse color by the diffuseMultiplier, and translucency color is simply multiplied by the translucencyMultiplier. In the UI, the multipliers are just 0-1 float sliders.