1984 Lincoln Town Car car stalls and lots of black smoke

My lincoln has been stalling out and when it does lots of black smoke comes out. Its feels like it chokes out, as if somthing gets clogged, it does this after about 5 to 15 minutes of driving.I replaced the catilitic converters, mufflers, fuel filter(1year ago) it did a little better after that but not much better.I replaced my vacuum valve silenoid and valve sensor flushed my engine because of suggestions from friends and that still didnt do anything.I checked my vacuum hoses and none of them were lose or cracked. It is getting very frustating. If you give help me that would be great!