This device is attached to the fuel system. I'm not sure what it is or what the setting should be. I found nothing on the web. It has dial settings 1 thru 5. The word PROFUEL is stamped in the back. I'm having trouble with the photo. I'll continue to try and post photo.
Sounds like a fuel pressure regulator for use with a fuel pump.
Does it look like this? If so, John is right, it is a fuel pressure regulator for use with a fuel pump.