Rattling sound and dropping RPM

This could be a number of things, but I am going to suggest we start with two things. First and foremost, we should check for codes even if the light is not on.

Here is a guide that will help with this:

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

If there are no codes, then we should check and see if there is a vacuum leak. I suspect this is going to be the issue so here is a guide that will help with locating it:

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

Depending on the results of this info we can also determine what is happening by watching the o2 sensor data. I am attaching a guide that will help with determining what the short-term fuel trim data means. I suspect this will show it is lean and if that is the case then we do have a vacuum leak or low fuel pressure.

Here is a guide that will show how to check fuel pressure:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Please see below and let us know what you find with this, and we can go from there.

Thanks