the main problem is you should always decarboxylate your weed before you cook with it. Decarboxylating is the process of converting THCA into THC. As many of you know raw mj contains THCA, which is then converted to THC when it is smoked. If you do not convert the THCA ahead of time then you rely on the cooking to heat up the THCA enough to convert it.
My decarboxylating technique is to put your material in an oven at 230 -250 degrees Fahrenheit, do not go over 260 as just over 280 you can start vaping the thc right out of the nugs. I usually leave mine in from 30 to 45 minutes, when you take it out you'll notice the weed is a little dryer. Just add it to the oil and your all set. Soy lecithin is a great emulsifier and i also use it when making all my edibles as well