Whats problem with my model faces. I have tried all Normal faces, recalculated inside and some time outside yet to not get success. My file is attached and a screen shot i hope there is addon that can make everything clear
In places, where you see darker shading, inner faces are to close to outer faces. Try to get better geometry (similar to the other side of your object, with smooth curve in upper corners) and then use solidify modifier, but if you don't want to repeat this process, you can just set Transformation Orientation to Normal and pull inner faces in problematic areas a little more inside or outer a little more outside.
You have some faces double each other in the same position, which causes the ugly Z-fighting effect. Delete one half of your mesh (I noticed that the model isn't symmetrcal). Remove doubles with W-->Remove Doubles and increase the Merge Distance to the value above 0.01.
Add a Mirror Modifier and apply it. Apply transformations (Ctrl+A-->Apply Location, Rotation, and Scale). Add Solidify Modifier, increase the Thickness value, check the Even Thickness checkbox and play with the Offset value to get rid of the ugly results.
I found the good solution maybe ever body like it. After doing flip normal, recalculation inside and outside. Try this
select the model in edit model press N to open the panel go down in shading section --- just check mark ------------- "Backface Culling" .!!!!!!!!!!!!!!! thats it...............