1995 Other GMC Models Van runs rough

I have a 1995 GMC 1ton Vandura 5.7 liter, recently I changed the spark plugs & wires. After doing this I started the van and it stareted fine and idled fine but when I pushed the gas pedal down it would start to sputter and want to stall. So the problem seemed to happen just upon initial acceleration and if the van didnt stall it seemed to run fine while driving but when I'd come to a stop and start to accelerate it would start to sputter again and I had about 50/50 chance that it would stall. So then I replaced the fuel filter and started the van and still had the problem plus I noticed that black smoke was now coming from the exhaust, also black liquid if I pushed the gas pedal. So then I replaced the distrputor cap and rotar, in which after this I'm having a hard time starting the van and all the other problems which I've discribed.