Ford Explorer 98 4*2 does not revolutionize when you put veloc

Hello, first of all, greetings to everyone on the forum. My problem is that my 1998 Ford Explorer takes a long time to start. When it does start, the engine runs unevenly but stays running. There comes a point where it responds very well to acceleration, but when I try to shift gears, it stops revving and has no power to move forward. It's a truck that was recently tuned up.