Runs rough and misfiring

First the not revving past 4,000 RPM's sounds normal because these engines have a rev limiter on them so you don't hurt the engine.

When driving and it acts like it misfires, is there a check engine light? Let's pull codes if there is. Here is a guide on how to do that:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

If there are no codes, it sounds like you ruled out the ignition system for now. Let's address the fuel issue next. Hopefully there is a code that can point us to a specific cylinder. Again, if not here is a guide that will help:

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

If we don't find anything here, we may not have a misfire but instead a vacuum leak that is causing the engine to run rough. Here is a guide that covers these items:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let me know what you find with all this info and we can go from there. Thanks