I have a 1993 Corsica with the same engine. I bought it for $360 a year ago. I’ve had to replace one coil, all the spark plugs and wires, one injector, the ignition module and installed an intake gasket set. When I bought the car, it was literally running on two cylinders and would only idle. It runs pretty good after making a ALDL to USB adapter and adjusting the throttle stop back to factory specs. Although I still have antifreeze getting into the oil. It doesn’t mix with the oil but it does come out of the drain plug first indicating it’s not a head gasket leak. When I replaced the lower intake manifold gaskets I didn’t know to use new bolts with thread sealant and I think that’s where the antifreeze is leaking into the crankcase...

 

With all that done, I’m averaging 24.5 MPG. It should be better than that but I’m still working on it.

 

This car was my brother in law's dads car and it was given to my brother in law in 97 when he graduated high school the car is still like new and the only major problems they've had was a head problem back in the early 2000s and all that was was the valve guides leaking oil my brother in law said he was averaging around 26 with it until he parked it for the fuel pump going down

 

Ok, that said. What’s the fuel pressure? Harbor Freight has a fuel pressure checking kit that’s not too expensive. Maybe the fuel pump is still bad or the pressure regulator may be bad. A compression check will let you know if the cam timing is off.