First off, are you sure you're dealing with a fuel modulator or is it a throttle delay? The terms are often comfused with one another.
If it's a modulator, the adjustment is really simple. But first, you need to make dang sure there are no air leaks in the supply line from the air box and that the seal between the piston and housing is good. Meaning, that they aren't worn out.
Unlike the throttle delay, if the modulator fails to actuate properly you will likely have very sluggish throttle response.
If all's well there, you simply have the governor stop lever in run position and fuel lever in full fuel. Put a .454 delay gauge between the #2 left bank injector body and rack lever.
Rotate the modulator lever clamp on the rack so that the roller on the lever contacts the "cam" lever that pivots on the modulator housing. Ensure the gauge is firmly held against the injector and tighten the clamp (gently now) and remove the gauge.
All done.
Good luck