1991 Toyota Paseo engine problems

Process of elimination.
Keep track of each part you swap with as you move forward.
Start with the easiest parts to swap with another cylinder

Swap the spark plug wires to see if the misfire follows
swap the fuel injector. Inspect the distributor cap closely specifically with the cylinder one terminal.
Then move to mechanical
such as camshaft, rocker arms, valves.
Have you done a leak down test on each cylinder

Was the compression even on all cylinder (200psi on all four)?

Swap parts to see if the misfire follows and do what I recommended in the last post.
You may want to do a leak down test to make sure your combustion chambers are sealing well.
It is not consuming fluids is it? Engine oil, coolant.