What is the problem. Changed a lot of things, but still have cylinder 8 misfire

Define "changed a lot of things".

Compression test cylinder 8. You might have a burned valve or worn piston rings. If the compression is very low the cylinder won't fire. Hope that helps! Jim

I changed wires, throttle body, plugs, ecm, egr. All injectors are good, fuel pressure is like 60+ psi, all ignition coils are good. Haven’t done compression test yet.

The mystery is that when i reset the codes and drive, the check engine light stays off. When i stop at a light and idle it comes back on. As long as im driving it wont come on. Only when at an idle, and the engine warms up.

If everything is new and working properly as you claim there would not be a problem. What is the actual trouble code and what have you done?

Hmmmmm, well if the engine was truly misfiring you'd have a definite shaking and a chugging sensation, especially on acceleration. Put your hand near the tailpipe. You should feel a steady flow of exhaust gases. If you feel and hear a rhythmic "putt putt putt" from the tailpipe, the engine is misfiring. It is possible and does happen from time to time that the PCM will pick up some vibration that triggers a misfire code. If the engine is not misfiring but it throws a trouble code P0308 (misfire on cylinder number 8) or a P0300 (random or multi cylinder misfire) the PCM is picking up something else. If this is the case it's best to visit your local Dodge Dealer. This may be a known problem for your vehicle and the Dealer will have a service bulletin on it. Hope that helps! Jim

That is the exact code and the exact sound from the tailpipe

It runs fine except for idling. Then its rough.

Just in case it is a sticky injector try a good fuel system cleaner.

I’m 100% positive its none of that. Just drove to work and the whole way here the engine light has been off. No trouble codes. But I’ve got this sound coming from the front like a helicopter makes (whomp,whomp,whomp) as i go straight, or turn the wheel to the left. When i turn the wheel to the right it stops. I’ve got a 4x4.