That would be US or French maximiser kit. Stevef is spot on. Gear down, one engine out, you are better off with no doors. Gear up, engine out, you are better off WITH the doors. Used to have to use separate performance graphs for each configuration, even with both engines operating, for take-off distance on limiting runways, and for single-engine climb rates "in the event of ". Difference was in all honesty so small that we (Intra) dispensed with the doors at the first sign of degradation in service.