You have to realize that once you foil, you are switching cooking processes to one which is essentially braising. It will soften the meat but at the expense of the bark.
One thing you could do is to cook as normal, pull the pork, put it all back into a pan and smoke the pulled pork itself for awhile. While that won't get you any more bark, it will make the bark you have a little crunchier, and it will add smoke flavor to meat pulled from the inside.
seattlepitboss
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