your shader is not set up to work with gamma correction...  there is some math involved..  I think (specular + Diffuse < 1)  when using GC & IDL.  

Shaders designed for older versions of poser dont look good with IDL and GC however if you look into snarlygribbly's scene fixer it can correct some of the cludges that were used in earlier version of poser that are no longer necessary and now produce undesireable results