DXM and bupropion isn't, as far as I know, dangerous- it's just that bupropion effectively suppresses the CYP2D6 enzyme in your liver, resulting in almost none of the DXM being converted into DXO causing you to have a different, much more intense trip.
Once upon a time I was put on bupropion while still very interested in DXM and I carefully experimented with tripping on bupropion + small amounts of DXM. It's quite unpleasant, very, very psychotic, very stimulating (I stayed awake 48 hours like it was nothing and it often took another 1-2 days to sleep normally) and highly visual, with little in the way of traditional NMDA bodily effects. Around 60mg produced threshold effects (I was about 75kg at the time), 300-400mg produced effects as strong, if not stronger, than 1200mg DXM w/o bupropion- complete ego-loss, forgetting what 'I', 'have', 'taken' and 'drugs' meant, profound psychotic thinking (believing I was controlling events with my mind, believing I had developed all sorts of psychic abilities), 'astral travelling' (closing your eyes and imaging worlds so engaging that you forget that you've got your eyes closed and are imaging everything), true OEV (movies in the clouds, power pylons walking across hills), it was the closest thing to actually having schizophrenia I've ever taken.
It was very similar to 'plateau sigma', but without a 'forth plateau' trip fading into 'sigma'- I think that DXM has a far longer halflife than DXO so, through repeated dosing, it is possible to accumulate enough DXM in your system to continue tripping after the effects of the DXO fade.
In any case, it takes about 2 weeks for that shit to fully clear out of your system- most of it is probably gone after a week, but it can't hurt?