Hi Richmond,
the behavior is caused by the DI API logic from B1.
So why don't you just take out the warehouses from your data mapping?
The DI API logic will automatically fill the existing default warehouses depending on your B1 settings of the receiver system.
Another option is to use a "Value Mapping" within B1i to replace a specific value for a defined parameter. For usage please check the B1i embedded Help.
Best regards
Bastian