I dont believe the MS2/micro has the ability to handle a raw knock sensor signal directly and do anything valuable with it. That processing, filtering, etc is done externally and the Micro just receives a digital yes/no input from the external source.(or an analog 0-5v, but still same theory)
It been a while since I was using and looking into the knock sensing for MS2/micro, but that's what I seem to remember. The MS3/micro has more ability, but is still limited compared to more advanced and refined knock sensing that is more common in todays factory controllers and some of the higher end standalone knock sensing devices.
DIY Autotune should know for sure what your options are and normally great for support.