The speedometer could be related to a vehicle speed sensor and the rough idle could be nearly anything. For example, low or high fuel pressure, an engine vacuum leak, or simply in need of a tune-up could cause the rough idle.
What I recommend is to have the can-bus scanned. It requires a scan tool that can communicate with all modules. Here is a quick video showing how it's done:
If you look below at the two pics attached, they show the can-bus system. Basically, all the modules/computers are tied together via a couple of wires. By performing this type of scan, it should identify any codes present regardless of the module. Hopefully, this will point us in the right direction.
Let me know if this is something you can have done.
See pics below.
Images (Click to make bigger)
Sunday, April 18th, 2021 AT 8:15 PM