PIP seems to be highly variable between individuals, and sometimes defies logic. Carrier oils, esters, compounds themselves, solvents/solvent concentrations, genetic nerve density/sensitivity in certain injection sites... the list goes on. I rarely get pip, but every once in a while the same stuff I've been using for weeks or months, injected into a site I've used for decades, will for no good reason be sore for days. Sometimes trial and error can rule out some of the previously listed factors, other times it seems to be an act of God.
Do you have a lot of experience with Deca?