Quote -  you're double correcting and not linearizing, i think.  the first power function should be to 2.2, not 1/2.2. 

Precisely so. Plug the output of Math_Functions_3 directly into Value 2 of Color_Math_4. Change nothing else until you've rendered that!

Edit: well, you could put the Diffuse_Value back to what it was originally...

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)