How many items have you stacked on your OBDll port with no issues? Most items make an adapter to plug into the OBDll port so you can still plug something else into it. Aux fuel tank, 2 low kit, performance box just to name a few. Of course they all say to plug THEIRS into the actual OBDll port and plug your other item into theirs. Whats the limit? What have you stacked and in what order?