Should be easy, even if you don't have direct power adder tables.......Lets use some random numbers. Let say your total fuel flow is 400lb/hr and you need an extra 100lb/hr for the nitrous. That's a 25% increase in total fuel flow. Now of course you will likely need to ramp that in based on time, rpm, something........or have a separate fuel table with 25% added starting at any rpm above where nitrous comes on