i know what you mean man... the only time that happens is when you torch the weed for too long, and you inhale BURNING HOT smoke. that fucks up your throat, making it build up some liquid. thats why you get the feeling of suffocation (and im pretty sure you COULD actually suffocate like that). the high is not any more intense than any other high, but because you have problems breathing and shit you get REALLY paranoid and start having a bad trip. try and keep the smoke somewhat cool when you inhale it, and this wont happen/

edit: at least thats the only time it happens for me, im sure it could also happen from allergic reactions and what not though...