[75 911s]

First off, I'm sorry for your setback. Very good thing that you caught it quickly before more damage occurred. I use the same LED bulbs. I doubt it's the diode directly, If anything I would think it might be when you swapped the bulbs out, they way the instruments are grounded is critical. Also the individual bulbs, some have cardboard insulation sleeves if I remember.

There are also big grounds running off a lot of the backs of the gauges. Did you have all the grounds installed before attempting to connect to power?

Ebay has a nice large laminated color coded diagram. It's way easier to read and follow. I recommend getting those for your year.

Check all your Earths, at the battery, at the engine, at starter, and the main one in that harness.