Wiring help
 

So it all started on Monday drove my 1993 Miata to work just fine no issues. Went to lunch still no issues, but when I went to leave I noticed my idle had dropped to a cool ~400 for some reason and my radio (aftermarket Sony xav-ax1000) stopped working and the home button on it was blinking for some reason. So that was odd but I thought I found the solution to my idle being that one of the screws to my bmw tps had vanished so I got a new one and am going to reset it in tunerstudio this weekend. But here’s where it gets weird if I have my car idling and I turn the map lights on my idle will shoot from 400-3000 and I have no idea why. Current plan is to rip my dash apart looking for and faulty grounds but any knowledge about what else I could be looking for would greatly be appreciated.

In these cases my first inclination is to re-check the last work I did on the car, for loose ground bolts, connectors not properly shut, and other things I may have rushed, forgotten about or just plain got wrong.

BTW, welcome!