I have the same problem. Infill is good, perimeters/walls are good, but for solid infill too much material is used.
If I reduce the extrusion factor, the material used for perimeters and walls is too few.
When I manually reduced the flow while printing to 65% the result during soild infill was much better. So the difference between extrusion length during solid infill and perimeters/wall must be really large in my case.
Sometimes after solid infill the surface was that rough, that I had problems with step loss...
Is there a (easy) way to get it fixed with post processing scripts?
thanks
Soeren