I once heard the dumbest idea ever from a student. She suggested that the STEP won't test FA 2016 until later in the year, because it just came out.
Reality check: FA catches up to STEP. STEP is not waiting for FA to make moves. I have read both versions and will admit the differences are minute. The "differences" you are talking about could have been on STEP exams long time ago.
You are very close to you exam, like me. Don't start opening fresh textbooks is my opinion. Also, some of the changes are reflected in Qbanks.
Good luck.