I'm assuming you get DTC P0306? Are there any other codes??? Also assuming the replaced RCM is new?? If not that could be a problem.
1. check the ground just in front of the battery, It is sorta under the fill tube for the window washing fluid is clean with good connections. There are four brown wires connected to the fender there. It is a ground for most things Power Train Control.
2. Look back through your records and be certain the Crankshaft Position Sensor is a Bosch.
3. Under the car there is a inspection plastic on the "bell housing" that allows inspection of flywheel/flex plate. The CPS gets its signals from the flex plate. Hopefully it is clean.
Those above could effect any knock signal, but with yours always specific to the #6 cylinder you should consider moving #6 injector to a different cylinder and see if the knock DTC follows the injector. Pull the plugs on #6 looking at their condition and inspect the cylinder with a bore scope. Gape on plug should be .040. While plugs are out check compression on #6 cylinder.
4. There is one knock sensor per engine side and they are hard to reach.
5. Electrical diagnosis gets involved and more than can be described here.
6. Make sure the serpentine belt isn't slipping.
GOOD LUCK.