If I were you, I'd test the compression to see how the engine is doing. Then stage 0, which is tune up, wires, plugs, oil, coolant, transmission oil, etc, making the car runs like it suppose to first. Then, buy fuel pump and wideband sensor.
After all that, and $$$, I would start looking into upgrades.
After all that, and $$$, I would start looking into upgrades.
