This could be the lowpoly affecting the AO casting... try setting the lowpoly to not cast shadows. http://wiki.polycount.com/AmbientOcclusionMap#Object_Properties_Method
Hi! When I checked the cage preview in Painter (exaggerated values for illustration), it looked skewed, sort of in alignment with your bake results. Then checking the lowpoly in Blender, the shading of the lowpoly looked funky (left). Once I discarded the meshes custom vertex normals the shading looked as expected (right)…
Hey guys! This is my first lowpoly modeling tree using max and following the technique of Damian Lazarski I'm happy with the result & hope you like it :)