Good Day
From America's Hundred Thousand, the basic weight of a P-38J is listed at 12,780 pounds, a P-38L is listed at 12,800 pounds. However, the empty weights of both machines are 14,100 pounds. Empty weight is equal to basic weight plus the weights of trapped fluids, ammo, gunsight and camera, drop tank provisions, oxygen equipment and other equipment. I don't claim or infer that the dive flaps and aileron boost units totaled 20 pounds in weight, but checking out the sources used in AHT may be of value.
Eagledad