Early 99 motor problem -_-

[TxRanger3006]

Ok I have an early 99, my problem is that when I drive at highway speeds for a fee miles or romp on it to pass on the highway, my truck will get a low sick idle. If I have to slow down when that happens il get a lot of vibration when accelerating and it doesn't wanna go above 40 mph. The last time it happened I tried to push it to get home and every mile I went it got harder to go anywhere, I would have the pedal to the floor with a bunch of black smoke but only go up to 5 mph. Then it just died and I got pulled home by a Chevy . I got an hpop, valve cover harness and new ipr pig tail but wanted to see if there is anything else I should look at that could be the prob. Thanks in advance