Firstly, at 150 lbs, you will not be able to tell the difference between 110 and 120 psi. Secondly, how are you measuring the pressure? Few gauges are accurate enough to measure the difference between the two. Thirdly, few pumps that indicate pressure over 100 psi are actually even capable of achieving these pressures on a reliable basis. I generally recommend the thumb hard rule: if you can depress the tire with your thumb add a bit more air. The stronger you are, generally the heavier and stronger rider you are: hence better return on harder tires. The weaker you are, generally the slower you are and less punishing you are on the tires.

As for the pressure limits of the MA40, you are perfectly safe at 120 psi.