Help, renal physiology

I am in big trouble, our physiology dept. gives practice exams before the real test, and I did real real bad. I have the guyton, stars, brs, the koeppan book (mosby series), and of course the class notes but I don't have any exams. I have asked my classmates and they have the same problem as I (not having old exams). I am really frustrated because I went to all the renal lectures, studied before class and after and did all the brs question yet I sucked big time in the practice test. Please if anyone knows any sites with questions or anything but not any more books ,I have ran out of money.