If it's the PDK I think you're using, there will be a separate symbol for monte carlo than for conventional simulation. This is a rather strange design choice by the creators of the PDK, but what most people do is to use the "_mis" or "_mac" (depends on which version it is) flavour of the devices all the time - that way you don't have to keep changing them back and forth.
If you do that, then it will work in all simulations, with no need to hack anything. You should be able to do a find and replace to change the devices. Or a bit of SKILL code.