P0302 cylinder 2 misfire

[IndestructibleYaris]

Unless you do your own thorough diagnostics, I can't comment on another mechanic. Resistor type spark plugs were implemented after the dawn of electronic ignition around the 1990's. These resistors can go bad inside the spark plug leading to an open circuit that destroys the ignition coil. Your car could also be running horrible, thus destroying a good spark plug. Most mechanics are taught the wasteful technique of replacing systems rather than the individual component that has gone faulty among the group of otherwise perfect parts. This is done because most people do not understand diagnostics or the value of knowing the truth, and the experience of learning that comes with knowing the diagnostic truth.

You will never know the quality of a mechanic until you're more skilled than the man you're judging. Otherwise, you are just guessing. He knows tricks to diagnostics that you've never considered.