Ford - Ranger :: 2000 - Speedometer Quit / Jump When Brake Pedal Pressed?

I have a 2000 Ford Ranger, 5spd with 3.0 v6. The speedometer will jump around or quit about half the time whenever you push the brake pedal or use the turn signals. I've cleaned all the grounds I can find including taking the battery cables off the clamps and cleaning them, and I had to clean all the fuses (inside box and outside box) because most of them were corroded. It still does it. Occasionally, I'll hear a buzzing/crackling noise like electricity arcing when I use the brakes or the turn signals which sounds like it's coming from the left side of the dashboard.

I took off panels and the fuse box, but I don't see any sign of arcing. Also, the noise only occurs when the truck is actually moving, never when it's sitting still. Also, the engine has a slight flutter at an idle. I hooked up a computer, and the O2 sensors were erratically jumping between rich and lean, so I replaced all of them. It says Insufficient EGR flow detected, so I did put a new EGR valve on and cleared the codes, but it still reads the same. And lastly, the computer refuses to finish either of its diagnostic tests. I've tried the Koeo and the koer tests, and neither will complete.