cpu override

I ran some searches and nothing came up. If this is an obvious question, please be gentle, I'm new here. I posted this in electronics and got almost 100 views, but no replies. Years ago I had a Ford Focus SVT and a popular after-market item was a device that plugged into the diagnostic port...

I ran some searches and nothing came up. If this is an obvious question, please be gentle, I'm new here. Years ago I had a Ford Focus SVT and a popular after-market item was a device that plugged into the diagnostic port which allowed you to put temporary over-rides into the CPU -- the most...