fit2inspect,
I recently passed the ASME Section IX/B31.1/B31.3 endorsement exam. I couldn't find a thing in terms of study guides or sample questions, so I just read through the code books a couple of times and tabbed the major subdivisions in each and got familiar with "what was where". My test was a total of 55 questions, broken down as follows: (15) qualification, (13) fabrication, (10) materials and design, (2) definitions and terminology, and (15) inspection.
There were a few real difficult questions that I ended up guessing at, but there were also a few "gimmies" as well. An entire exam on B31.3 will certainly be more involved than what I took, but how the categories are weighted should be similar. Remember not to focus on facts or memorize the code book, but have an idea of where to find the answer quickly. Time becomes the real issue in these exams. Don't mess around searching for something you can't find at first glance - skip it - chances are you'll run across the answer while looking for something else!
Hope this helps. Good luck!