When my knock sensor was bad, the engine was a lot more powerful on moderate revs during warmup. I'm always at moderate revs during warmup (sub 3k).
I could feel how power changed between good and bad, probably when the temperature reached the point where it goes in closed loop, like it was going in and out of closed loop in cycles of say 5 seconds. After replacing the sensor it is less pronounced, but definitely still has more torque during warmup. This is probably a result of Warm-up volume increase correction. Surely it is possible to tweak the sensor resistance to fool the ECU. But I guess it also decides when to engage the TCC, so it would ruin milage, and probably not be wise to use during longer periods. Wos has this mod on his dragstrip 626 though.
1998 Xedos 9 2,5 MT (5-speed)
2000 Xedos 9 2,5 AT
2002 BMW 530i Touring stickshift
Originator of the Mazdaworld Old Boys Team!