My suggestions:
If you are just starting your tests now for the April exam, it might be worth it to just stick with all the AAMC tests.
However, if you are taking it in august, and have time for more tests, I'd recommend using Kaplan full lengths and then moving on to AAMC full lengths.
Or if you use TPR exams, use their 4911, 4921, 4931, etc. Their test A-D are the hardest material they have and generally crush a lot of people. The test centers here don't even advocate giving them out because they feel they crush the students confidence too much.