1991 Quits running

I'm a new member looking for some help. 1991 Ranger 4cyl 2wd manual trans. 250k miles. Driving down the road it started cutting out, real bad, sometimes quit running altogether. Turn the key off then restart no problem. Got so bad you couldn't drive it. It would only run a few minutes then stop. To restart you always have to turn the key off. I changed the fuel filter, spark plugs, wires, fuel pump, both coil packs, crankshaft position sensor & ignition control mod. Still cuts out. Water did get into the cat converter & muffler due to flooding. Also has a check engine light. Last time I had that it was due to low coolant. Anyone have any suggestions?
Thanks