I know that PsXbox supports this, and am surprised not to find it in ePSXe.
I'm basically looking for emulator-side, software-based turbo settings. For PC game controllers that don't include the feature or who's drivers that might set it are inoperable. PsXbox not only has the feature, you can set the delay.
It's also possible I'm just not seeing it when it's right in front of me. If so, would some one biff me on the head and point the way?