1991 Toyota Pickup losing power, not running at idle

I was driving yesterday and my Toyota pickup started losing power. If I let off the gas at a stop it would rapidly die. I managed to get it home but had to floor it just to get it going in 1st and 2nd gear, and if it was in neutral it would die without giving it a lot of gas. The only way it will start is if I give it a lot of gas while turning the ignition, and have to keep the RPM’s up to keep it running. Looked under the hood while it was running and when I let off the throttle the entire motor would shake violently. Cant tell if it’s just not getting fuel correctly or if it blew a head gasket maybe. Seems like it might only be firing on 2 or 3 cylinders. Any thoughts would be appreciated.

In 1991, some of these trucks were fuel injected and some still had carburetors…Which flavor is yours? I wish mine looked as nice as yours !

First step might be a new fuel filter, check fuel pressure and fuel flow…Then pull the plugs, examine them, do a compression test…

The problem may no spark or erratic spark in some cylinders. If you have a distributor, there’s a pickup coil, also called signal generator, that basically does the job that points did in older, pre-electronisc distributors. It tends to fail when hot, at first occasionally and eventually completely. That happened to my 1979 Toyota pickup (RIP).

Is the check engine light on? Have the diagnostic codes been retrieved from ECM memory yet?