1990 Buick Lesabre hhheeellllpppp

I have a 90 buick lasabre that I have been working on for a week now. I am an intermediate mech, spent some time working in dealerships, so I am knowedgeable on mechanic work. It is stalling on me going down the road, sometimes after long drives and sometimes after a very short drive. First I replaced plugs, wires and fuel fillter. Then when that didn't fix it, I checked the fuel pressure. With a fuel pressure guage connected, i'm getting 43 psi w/ key on which is spec, so it's not a fuel pump. I checked for spark at the wires and nothing, so I replaced the coil pack and had the ignition module tested at the parts house and it passed. So I went to the crank sensor and replaced it, and after that it drove great for about 10 miles, then stalled again and will not crank. When it stalls and won't crank, i'm not getting fire, but when the car does work, I have spark, so something is cutting my fire off, what's left?