FreemindFade -
I think you may be taking the answer out of context. Comey was referencing if the Department of Justice could stop an investigation. He was NOT saying that Trump had never asked him to stop an investigation. Here's the transcript:
HIRONO: So if the Attorney General or senior officials at the Department of Justice opposes a specific investigation, can they halt that FBI investigation?
COMEY: In theory yes.
HIRONO: Has it happened?
COMEY: Not in my experience. Because it would be a big deal to tell the FBI to stop doing something that -- without an appropriate purpose. I mean where oftentimes they give us opinions that we don't see a case there and so you ought to stop investing resources in it. But I'm talking about a situation where we were told to stop something for a political reason, that would be a very big deal. It's not happened in my experience.