if its knocking that much at 3000rpm on light load id say a sensor is loose or something near the sensor is loose
if you can replicate the knocking at 3000rpm or just below and have time to do a map tracer via MONITOR, MAP TRACE and press UP once on this screen, try and pinpoint which cell it is using when it knocks around that level. you can then view the cell values for IGN and INJ under SETTING, IGN or INJ. obviously its a bit fiddly and sometimes best left to a tuner, but if you have patience and are interested you could try that. perhaps the cell it's using has some wierd timing (unlikely but possible) otherwise id say something mechanical is loose
if you want to debunk the ignition timing / fuel / load etc drive the car, replicate the knock levels you are seeing
then goto SETTING, INJ/IGN and back out 5deg of timing, so you make IGN -5 and then continue to drive around
check out the knock values then, if its still knocking the same levels id say your issue is mechanical noise the sensors are picking up
if the knocking stops when you back out 5deg post up here and we can look at what it might be (fuel, mapping, something else whacko)