This could very easily be a clogged fuel filter. It acts like the fuel pressure is too low. There's enough gas for lite throttle, but not enough for load. Also, it could be the fuel pump itself. But why not start with the cheaper filters. Check the fuse for the fuel pump too. It's obviously not blown, but these older fuses get corroded in their sockets. That can cause an intermittent failure or a lowered supply voltage to the pump. The fuel pump uses quite a few amps, and any resistance could cause lowered fuel pressure. A good shop can measure the fuel pressure. And then of course, it could be something entirely different. Injectors, throttle position sensor, high tension wires, and on and on. Good luck.

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