Just figured I will share a story with my internet bros who have helped me out so much through the years.

Car:
2005 Mazda6 S SportWagon V6

Symptoms:
- Flashing CEL
- Rough idle
- Loss of power

Took it to a local mechanic for the CEL. They suggested a tune-up, but I wouldn't hear it--spark plugs and O2 sensors are new. I told them to tell me what the engine code was. They charged me $15 for the "diagnostic". Came back with 304 - Bank 4 Misfire. They suggested I need a new ignition coil, they didn't have the part and I would have to come back the next morning for the repair.

I got back home and decided to check out the problem myself. Took the ignition coil out, it was covered in a white crust. I knocked it against the car a few times to loosen the crust, took some canned air and blew out as much of it as I can, and stuck the part back in.

The car now runs perfect, and I saved myself $80 in parts and labor.

Lesson learned: A lot of "broken" parts are just dirty.