Even though you know the dealer, did he grow it? If he didn't then you don't know what your smoking. Personally I have alot of adverse reactions to the shit they put in bag weed. There's all sorts from grass to industrial oil to nail polish. I have been stoned like that before, almost fucking died in my friends shed. Put me off weed for along time but considering the fact he smoked pure skunk I wasn't suprised I got fucked. Felt extermely nervous and I couldn't control my face for like 10 hours after smoking. If you don't have a tolerance and your smoking some of the newer really potent strains then you will get hit like a bus. Some people are more prone to the negative effects anyway so you just have to control how much you smoke or build up a tolerance.