The one on the left (bent up) is now junk.
There's not an easy/good way to test O2 sensors. And, with the price of gas, and how much Stangs drink gas, there's no good reason to reuse those sensors.
As sensors age, they run the engine richer. This "may" result in more power , but they also respond slower. IMHO, the slow *ss response time FAR outweighs the richer mixture and often results in less HP
Either way, older O2 sensors (after ~20K miles on our type) use more gas. And, often, they reduce the power of an engine on the street (since the gas pedal is just about "always in motion").
BTW: It looks like you're running lean on both sides. Did you get lean codes for both sides? Or, it could be additives making the white appearance.