Where is the knock sensor at?

Where is the knock sensor located, is there even one at all? Also can anyone tell me why you make more horsepower with 87 octane? I tried to run my car with 87 on an 80* day (with cast iron heads and 14* of timing) and it didn't knock or ping (plugs were fine too), but it felt way slower. I put 93 back in and it ran much better.

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88GT stock shortblock, GT-40 iron heads, Edlebrock Performer intake, 24# inj, Pro-M 75mm Bullet MAM, 3.73, hurst short throw, F-303, electric fan, alum rad, FMS HD clutch, R134a ac conversion, 70mm TB , and some other stuff I probably forgot, 13.02@106 with a 1.87 60ft