Ok my sister drives a 1997 Toyota tercel. A check engine light came on and she complained of almost a bucking sensation on the highway, so I drove it and indeed the car bucks at highway speed and struggles to run upwards of 70. We have replaced the fuel filter, and pump, it has new plugs coils and wires but it still has the same bucking feel on the highway around 60+ and struggles to run 70. I am truly stumped on what to do next. There is no EGR port to clean out carbon, so if anyone could help that would be incredible!

 

Did you try reading the code the CEL was giving?