Toyota Corolla 1989 1.6L Sedan carb 400 000 k's

I have been having problems with my car bucking at a high acceleration and then getting worse and worse as the car heats up and then when it was cool it would be go back to the not as bad problem. 2 days ago I tookm it skiing and on the way home it was doing it very bad and then I got home ands turned it off, a couple hours later I turned it back on and it will run very badly no power backfiring cylinder misfires cant rev past 5000 rpm will idle at 500 rpm and die constantly. When I went to the mountain right before I was about to start going up hill I stopped the car to let it cool and it was like it would not shut off it kept turning over for about 5- 10 seconds. I have checked the vacuum cleaned egr valve fuel pump dist. Could it be spark plug wires or plugs? I just put new plugs in about 5 months ago also the exhaust is pouring out black stuff onto the ground from the fumes like when I put in carb cleaner just stains the ground darker????