91 Chevy G20 runs rough?

[Marcin]

Hi ill try to explain this as much as i can, I have a 91 chevy g20 with a 5.7L v8 automatic Before winter it ran like a champ nothing wrong with it. Once winter came around it started to run really rough, now when i drive it, it seems like when i step on the gas it dont have so much power like it used to, it smokes really bad, smells like fumes inside the van and outside, today when i looked under the van at the exhaust is broken past the catalyc converter and when i put my had behind the pipe it sprays some i guess liquid that has specs of black in it and smells i guess like gas. Any ideas on what i can check here at home myself would be great, Note the exhaust was like that even when the van ran really good