This. I'm preparing for aptitude test in Anees Hussian (bad choice, don't join), they have told us the same thing. NUST's test is mainly composed of FSc, HSc, and ECAT outline. Whenever there are differences between FSc and HSc, my teachers point them out and there are more than a handful, so I suggest you study them both. Also don't forget to get a ECAT book to get a gist of questions you will face in the entrance test.
If you're preparing for an engineering course, then focus on mathematics, physics, chemistry, and finally Intelligence (IQ+GK). If computer science, then devour mathematics because there is no physics or chemistry. (You'll be essentially giving BA Mathematics test for CS.)