I haven't really heard anything about "charging injectors" and I am going to school for auto service/ engineering. And your 88 Plymouth Olfordtruck had a totally different fuel system on it. It probably had a throttle body injection system where it looked like the engine was carburetor but it would have a couple of injectors right there on top of the manifold. The air and fuel would mix in the intake just a like carb would. The fuel system on our rangers is a multipoint injection system where each cylinder has its own injector and only air is traveling through the intake manifold.