1991 Ford Escort idles rough/ no power

Idles rough and when you step on the gas wants to stall. There's what you call a pip signal and when you unplug it it willl actually rev up. When you rev it up it's like it's out of time. It doesn't have full power. I tried a used computer and it was worse. Then I figured out that the used computer may be no good. Also, when you rev it up the cat. Gets red hot instantly. There is alot of exhaust so I know it's not plugged. I've been told that it means its dumping fuel. I figure their right because it acts like it is out of time. Do you have any idea what that pip signal is actually taking out of the system. Any help will be appreciated, thank you.