timberjet
Master of the Pit
Those competition guys like that do get better meat than you or I would hardly ever see many times in our lives. That makes a difference as well. Unless you raise it yourself or your neighbor does for you like me.
Here is some good reading from our site founder Jeff. http://www.smoking-meat.com/february-7-2013-smoked-brisket-low-n-slow-start-high-heat-finish
The red flags were waving for me when you stated that a 12 lbs packer reached an IT of 160 in 3 hours. While you've verified that your internal temp was believable, I would think the box temp is a mile off.
He did trim the fat off one side. I don't know but for me it's low and slow all the way.
From timber's linked article:
"Place the brisket directly on the grate and let it smoke cook until it reaches about 160 degrees. You are probably looking at about 3 hours."
He recommended using a 10-12lb packer cut brisket in the recipe (mine was 12lbs). How does this square with SuperDave's statement about getting to 160F within 3 hours being a clue/warning?? Jeff's even had the entire fat cap on, untrimmed, which seems like it would slow temperature rise, if anything.
If your meat probe thermometers are accurate, the smoker temp being high or low doesn't matter. When you get to that 190-195 IT of the meat, then you can start doing things like a toothpick test and go by the feel of the meat instead of the temp.