Check engine light

I changed my oil I change the oil filter, I change the spark plugs, I change the spark plug wires, and I change the air filter. Truck is doing better. But when I am on the freeway usually is when this happens. I will be driving maybe at fifty miles an hour I will punch the gas pedal to pick up more speed, the check engine light will come on. Usually does not turn off until after I turn off the truck and turn it back on. I cannot afford to take it to a mechanic shop to have them put it on OBD1 to help me figure out why it keeps doing that. My question is what could it be that would make the check engine light come on after I punch the gas pedal? Because just driving around town throughout the day does not do it.