This link has a detailed explanation on how to improve readouts from the MAX31855 : HeyPete.com Blog - MAX31855 Temperature Linearization
I followed the steps using µV polynome values from Resources and got same figures as Heypete.
I was the able to both calculate a more accurate temperatures for the MAX31855 and also tranform readings using same IC with other thermo couple types like the J- type.
The graph displays how much the thermocouple polynomes adjust my MAX31855 readings in the interval -100 to 700 °C for a K- and J- version IC.