I had some very good chaparral, which I boiled for about an hour. It smelled like burnt rubber. I got pretty ill drinking it. I only had a few sips. When I discussed this with a local herbalist, I was told it shouldn't be boiled but just mixed with water at room temperature and after sits a while, it can be sipped. She said that boiling would bring out the resins that are toxic. I believe her!
Also, I have heard of recall of chaparral products due to death of users.