Closest I have come to a "Regrettable Mod" would be the ABL lighting using EL Wire. I had a 2010 1SS and wanted to finish the look. It required removing the door panels, cutting away at the door panel, cutting and splicing wires... a lot of scary stuff. The end result looked AMAZING, but there was a catch. I had to use 3 transformers that would normally run on AA batteries - one in each door, and one in the dash. Why is this a big deal? Those little boxes produced the highest pitched annoying sound EVER! No matter how loud the radio was, it would pierce through any sound. And it wasn't your every day high pitched, oh no. This one gives you headaches and makes your nauseous. I had hooked it up to come on whenever the light for the window switch would come on, so there wasn't a good way of turning it off.
Unfortunately, I lost her in a bad wreck. I'm riding high now with my new baby, but don't have any plans of using EL wire again...for cars at least
I'll finish the ABL the right way one day.
You can see my pics in post #10