Do the lights appear to be the same brightness when the toad is hooked up, vs , when applied when the toad is not hooked up . If the lights are not as bright, you may have power drop somewhere in the connectors from the coach or in the wiring through the toad.
Because all things being equal the lights when the toad is hooked up should be as bright as when the Honda left the factory.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.