I ignore porous bed free expansion cooling when I cook BBQ. You should too. "Porous bed free expansion cooling" is the geeky name for what causes the dreaded stall. If you have barbecued a pork butt or a brisket, you know that once it reaches around 160 degrees internal that it can stay at that temperature for hours before the internal temperature begins to rise again. That's called the stall. As the temperature of the moisure in the meat rises, it evaporates and cools the meat. The process repeats itself for hours as the moisture that causes the stall dissipates. When it's gone, the stall ends. That's why the stall lasts so long.
So many BBQ "experts" tell us that barbecuing meat shouldn't be wrapped in foil until it reaches the stall. However, the truth is, the stall is irrelevant and can be ignored. The point is this. If you wrap meat that you are barbecuing at some point during the cook, do it at a time that is right for the kind of meat that you are cooking. Don't go by some standard "rule" that is often repeated but never justified with facts.
Here is an example, a select brisket will turn out better if it's wrapped at a point sooner in the cook than a choice or prime brisket. Remember, the only meaningful reasons for wrapping are to preserve exterior color, preserve moisture, and speed up cook time. Select briskets don't have as much moisture content from fat as a choice or prime cut. Therefore, they should be wrapped sooner than the higher quality cuts. Less moisture and fat content means that you have to wrap sooner in order to preserve what little moisture there is in the meat.
If you are concerned about the possibility of too little smoke getting into the meat, use
more wood chunks, or use green wood, or run your fire a little cooler so more smoke is
generated. Compensate less time in smoke with more smoke while the meat is in it.
Ignore the stall. It's irrelevant. Think through what you are trying to accomplish and time
things based on those goals.