All right. This is the answer to the source of Pinkie Pie's energy and Pinkie Sense. Everypony remember the episode "The Cutie Mark Chronicles", when Rainbow Dash did her first Sonic Rainboom. Pinkie Pie got her cutie mark at that exact moment, and I believe that was when she received an infinite supply of energy. On another note, Pinkie Pie's Pinkie Sense is easy to explain. She is clairsentient, meaning she can feel the future, meaning she is psychic.
Please feel free to post your theories or try to debunk my theory. I'm not saying that my theory is correct, but this is my answer.