Intermittent misfire.

[Gusthebus]

Didn’t want to high jack the “misfire” post so I will start this one .
I have a 2003 Express with a 6l engine and 156000km on the clock.

When I bought it last October it ran like crap and I did a lot of stuff to it fix the issues, but now it misfires intermittently, yesterday it ran good lots of power and no check engine light.
Today the check engine light w came back on and runs like crap.

So far what I have done to it is, new air filter , oil change, new spark plugs, new plug wires, new fuel injectors, new fuel filter, cleaned the throttle body, ran injector cleaner through the tank.

I have a code reader but it is a simple one that only say random misfire.

What aim I missing.

[MountainManJoe]

your code reader doesn't do any live data? That would help a lot. What are the codes you are getting?

when you changed the plugs, did you visually confirm good spark on each?
You could also throw a pressure gauge on the fuel system.