The reason I came to this site quite a while back is I was having similar problems. What a wealth of knowledge here in so many places, the forums, the articles, and the great people here got me on track. Like most people, I was originally having tough meat because I was not getting the IT high enough. I thought I was drying it out, same with briskets. Wrong.
I certainly agree with several items posted above. I smoke PB's (and briskets) in an Smoke-it brand electric at 225, low and slow works for me. Put it in, set the IT probe beeper at 195, forget it until the beeper goes off. Sometimes at 10 hours, sometimes at 26 hours later, depending a little on size, but mostly on the particular chunk of meat. Every chunk is different. Most will be 16-22 hours for me, but I never know.
Then at 195, because each piece of meat is different, I start poking it with a instant read temp probe. ($20 at Lowe's) Gives me a feeling if it is done like poking butter or needs more cooking, along with giving me a cross check of IT temps in other parts of the chunk.. Need a little more sometimes, a lot more most times. I check it again in 30-45 minutes, repeat till done..
After I get it to where I want it, I wrap in foil and put it into a towel wrapped ice chest for least a couple hours before pulling or slicing. Because of unexpected circumstances had to leave one almost 5 hours once, it was still steaming hot while pulling.
Check out some of the finishing sauces for pulled PB for an even better flavor.
Good luck to you, and let us know how it works out. Every smoker is a little different just as all of our taste buds are a little different at different times...Keep fine tuning.
