hestiate/stumble in high rpm

[dasbrick]

what could cause a stumbling/hesitating in high rpm WITH black smoke and backfires. I am thinking rich mix, and that being vacuum related, but where to go from there? which vacuum line might be the culprit? Or is it something more evil, like the fuel pressure regulator?

[Geonovast]

Pull the vacuum line off the regulator and see if it's wet/smells like gas. This would indicate that the regulator isn't working, and seeping gas into the vacuum system.