setAutoWaitTimeout or timeout not work as expected

Hi,

I want to reduce the time of my scripts and after several tests I have observed that setAutoWaitTimeout does not work below 1 second. The doc says that it works in milliseconds but this is not what i observe...
For instance:
if exists("my_image_not_found.png"):
    [...]
gives 1.6 seconds to expires. I can add a delay, no problem with that but I cannot reduce the time, event with setAutoWaitTimeout(0) or if exists("my_image_not_found.png", 0).
Any ideas? Do I have to conclude that sikuli cannot find an image less than 1.6s and I cannot "timeout" this search feature?

Thanks in advance.
Regards