Neither new spark plugs, distributor cap, plug wires, distributor cap, nor fuel filter will help, if the existing ones aren't defective or worn out. Wires and distributor cap can be easily and inexpensively tested by removing them and using an ohmmeter. Plugs can be tested by both the same method, plus looking at the appearance of the electrodes. A lower resistance air filter might help a tiny bit. But orig equipment air cleaners are near to as low as you can go. I don't think it is worth the expense to replace the air cleaner unless the existing one is sufficiently clogged up to need replacement. The exhaust system is another story. You can buy exhaust systems that improve engine efficiency. However generally this is only at the cost of louder engine. You need to be careful. Companies claims about their high performance exhaust systems can be exaggerated.
A careful checking of the emission control devices, fuel injection system, and fixing any faulty operation, can make an improvement. My car mechanical experience is pre-fuel-injection age, pre-computerized control of ignition spark, and fuel. But I would have the fuel injection system checked out to make sure no injector is clogged. My understanding is that the computer system that controls fuel volume, as well as sparkplug voltage and timing, generally either works, or doesn't work. If it doesn't work, the car doesn't run, or runs really really really awful. In my day we used to check spark advance to make sure it was approximately right, and if it wasn't, we would replace the mechanism responsible for spark advance - generally that meant replacing the distributor. Adjusting it to specs required expensive equipment, knowledge, and time. When you could buy a new distributor for $30, it wasn't worth the time. These days, the "mechanism" is the central computer, which adjusts the advance with a built in computer program. My understanding is that either the computer is working or it isn't. while you may be able to upload new firmware, I could be wrong but ny understanding is that it the device rarely if ever decides to just change the program on its own, so that the advance isn't adjusted properly, or the spark timing changes. However you can check the quality of the spark-producing voltage and current output in the secondary. You will need an owner's manual with specs and some kind of automotive oscilloscope. In my day we had analog oscilloscopes. These days there are computer-peripheral devices you can buy that put the oscilloscope display on your computer. Generally you don't have to remove any wires to check this, rather, you just clip electromagnetic current sensors around the spark plug wires, and clip an alligator clip or push on connector to the correct connector on the primary. There may even be analysis devices that tell you if the secondary voltage is correct for your make and model. So you don't have to view a pattern on an oscilloscope screen and compare it with pubished specs. The device that produces the high voltage needs to be checked for the right voltage envelope at each spark, as well as the timing of the sparks. If the voltage doesn't reach high enough, fast enough, and fall off at the right speed you won't have the best spark for complete burning of fuel. In my day we had coiled-wire transformers and sometimes electronic devices to help, such as capacitors and a few transistors and integrated circuits. Today there are digitally controlled devices and I don't know exactly what is available.
Then there are the exhaust emission control devices. The exhaust re-routers and exhaust sensors. Incorrect operation of some of these can cause poor fuel economy and poor engine operation.
Instead of old-style mechanical (spark) distributors, which use a mechanical linkage to sense crankshaft position, newer cars may have electronic sensors to detect crank position, and fully electronic devices, digital devices, to send the spark, with the correct envelope, to the right cylinder, at the right time. There may not be a "distributor cap."