The problem with the perf and pof exams is that with most questions there a two answer that are correct, however, one being more correct than the other. Once you learn to accept that these exams are really more a comprehension exercise then you'll be halfway there.
With perf, read the CAP698 from cover to cover and understand the info contained. Over half the questions in my exam could be answered by reference to the CAP698 and I don't mean the piddly graph questions.
As stated before, it doesn't make a mouse fart's difference if you pass them all first time or not. Most employers don't care if you passed your IR first time. All they want to know is could I stand being locked in a broom cupboard with only this chap for company for up to 12 hours a day.
Good luck with your training.