Is it the fuel pump or my fuel filter?

Im helping a friend with a fuel issue causing low power and some occasional misfire. I know a fuel pump and a fuel filter will fix my problem but I don’t want to replace a pump if it only needs a fuel filter. How can I distinguish between it being the pump or it being the filter?

If you suspect filter, change it.
They get old, it's not parts changing to replace a filter.
You can try to blow through it once you have it out, but really once it's out why put the same old one back in?

Measure the amps draw to the pump,amps clamp or ammeter in series to pump see if it looks excessive,over 12amps.

As suggested above, fuel pump current can be used to infer if the pump is working too hard to overcome a restriction.

But to be completely honest, I've NEVER seen a fuel filter cause any kind of perceptible engine performance issue. I've measured pressure before and after, current before and after, but the differences were marginal at best. Never enough to cause a miss or low power complaint.

Like Noah said, change it if you're in doubt.

Tyler wrote: But to be completely honest, I've NEVER seen a fuel filter cause any kind of perceptible engine performance issue.

I've seen it on a 2000ish S10 with a "seems a bit down on power" complaint. No codes and the truck seemed to run OK, but it showed up on a timed 0-60 run. New fuel filter and the 0-60 was back where it should be.

I've seen absolutely plugged filters set lean codes and keep engines down on power, but I work on a lot of neglected cars.