I had very bad PIP on my first cycle similar to you. Started after 24 hours, lasted 4-5 days and I had to take Ibeuprofen like crazy to be able to move my shoulders if I pinned Delts. When I pinned Pecs the PIP was manageable. I did a lot of reading and like you say here it was basically inconclusive. I would listen to the guys on the forum, they are incredibly knowledgeable and if they say its BA related then I believe it is. I'm about to order from trusted sources here and I bet there will much less PIP.