Disconnected vacuum hose on a pressure regulator will increase fuel pressure?

Yes, a disconnected vacuum hose on a pressure regulator will generally lead to an increase in fuel pressure. The vacuum hose helps regulate fuel pressure based on the engine's load and demand; when it's disconnected, the regulator may not receive the necessary vacuum signal, causing it to maintain a higher pressure. This can result in poor engine performance, increased fuel consumption, and potential damage to the engine or fuel system components.