DXM is what you want. Just take the regular recommended dose or slightly above it from the box (like if it says a tablespoon take two but you don't actually want to get high on DXM so don't be chugging it less is better) do it like 20 minutes before you take your dose. I've extended the high of opiate trips for 2 days with DXM, just redose every couple of hours. Make sure you get the DXM with just DXM in it no need for all the other chemicals. You can also add white grape fruit juice too I guess and/or an antihistamine like benadryl and maybe pot, alcohol, benzo's, caffeine etc will all slightly help but don't go crazy you don't actually want to get high on anything else.