-1992 Audi 100 2.8 V6

Can anyone give me a clue as to why when my engine is hot it gives me alot of trouble starting? It cranks over fine but, it won't "catch." After a minute of cranking it will usually start and generally run real crappy and blow out black smoke. Today I tried to start the car when it was already hot and it wouldn't start. Finally with the gas pedal all the way down it started, and blew out alot of smoke. Then I had alot of trouble keeping it running on the way home. The car starts and runs great when cold though. This is a 92' Audi 100 with the 2.8 V6. Any input is greatly appreciated! Thanks alot,
-Matt