If you do not exit out of the app, kill it and restart, it will climb up and peak. The middle of the climb is probably the most accurate- IF you do concurrent tests without backing out. Need to back out and kill the app to get accurate measures.
If you have the N64 app, test out the following N64 games to test how powerful the chip really is. Hummingbird and Tegra 2 play the following games smooth (Tegra is very smooth):
NFL Blitz 2001
Golden Eye
Beatle Racing
Mario and Mario cart plays smooth even on the Incredible at stock speed, so not good games to test.