1995 Buick Century What is injector knock?

1995 Buick Century 6 cyl Front Wheel Drive Automatic 100K miles

My car wouldn't run for more than a few seconds. I took it to the shop and they said it was the fuel pump in my tank. I took it home and replaced it and it started and ran. I drove it around for 15 minutes and it drove fine. Then I drove it down a big hill and back up and it wouldn't reach 55mph going up the hill.

When I pulled back up to the house I could hear this loud knocking sound. On idling it sounded like a ticking that would fade into a knocking and back. I even heard a couple of squeals out of it.

It really sounded like something was very wrong so I pulled the valve covers but everything looked okay. Continued to run it and the valves all looked like they were running properly but the ticking/knocking was really bad. My neighbor said that a piece of a valve must have broken off. I compression tested all the cylinders and they were fine.

I need to mention that this sound was CLEARLY in the top of the engine. I tried to isolate with a hose and that didn't help, but I was trying to isolate it among the rocker arms & cylinders. Nothing, but if you took the hose away it sounded like it was right in front of your face, definitely not way down in the bottom of the engine.

I tore the heads off anyway and the pistons, cylinders and valves look like they're brand new.

Can an injector make that kind of noise?

edit: also found metal shavings in the oil, these are definitely new. It also would sputter out and die occasionally when I was trying to isolate the noise, and then more and more often right before I tore it apart.