Well then....I'm afraid I didn't really understand your question. So...let me speculate;
What you were trying to convey is that something has recently changed? I'm guessing that you start it...."idle" it up to 1400 and then...when you're ready to "roll" you pop it into gear and go. But...instead of just dropping to 1250...like it used to...it drops to 1100.
Is that close to what you meant? Because if it is....the problem...and the solution... might be quite different than what I first thought.
As I stated previously,these engines have TWO springs in the governor...the LOW SPEED spring...for "idling"....and the HIGH SPEED spring for all higher speeds. As a result...they also have TWO sets of controlling weights rotating on a shaft to counter balance the effects of the springs on the fuel control rod that goes to and operates the injectors.
From start up to...coincidentally...around 1100 rpm....the LOW SPEED spring is essentially pushing on the fuel rod to "idle" the engine. It's counter balance partner in this...the LOW SPEED weights...are spinning and pushing BACK against the spring to maintain the LOWER SPEED setting the operator has selected. But, when the operator pushes the throttle to select a speed somewhere ABOVE the limits of the low speed spring...a transition takes place.
At some point...usually around 1100 rpm....the governor control has to transition from being influenced by the low speed spring and weights and the HIGH SPEED SPRING AND WEIGHTS come into play. As the throttle is advanced, there is GAP that is crossed. That's what Detroit Diesel calls it...the GOVERNOR GAP setting. It is the place that NEITHER the low speed spring NOR the high speed spring is actively "pushing" on the fuel rod. If that gap is not properly adjusted...it COULD cause the sort of symptom you are describing.
I say COULD because it isn't the ONLY thing that could cause your complaint. It could be that the engine is simply down on power for whatever reason...IE: dirty injector(s)... clogged fuel filters...low fuel pressure...poor quality fuel...and the list goes on.
Also, my "example" is for a single shaft and weight set governor in the later model engines. If your engine utilizes the older...twin shaft governor, the concept is somewhat the same but the "gap" setting is dealt with in a much different manner. You will need to consult the manuals you have on board and compare the information to your engine to be sure you are approaching your adjustments in a logical manner.
You should first go through a "loss of power" checklist before making any adjustments to the governor. Replace fuel filters...check fuel pressure and "spillback" for presence of air....clean or replace air induction filtration....ensure there are no exhaust restrictions.
If any of these terms or tasks are unfamiliar to you it would be in your best interest to "bone up" on them as they are the essential components to keeping a Detroit running in the "sweet spot".
Good luck.