Overheating, profuse sweating, hypertensive crisis, mass confusion... all that fun stuff. One problem is that DXM can mimick some of the effects of serotonin syndrome (although to a mild extent) so this could lead the user into panicking over nothing. Why would you consciously choose to take the combo? This is super risky if you ask me and 20mgs of MDAI isn't gonna really add anything. Overall though I'm guessing you'll be fine should you choose to take no more MDAI.