I've used SDK's ,programmed to low level controls, databases, etc, and created user and developer interfaces for years. But, I have no specialized knowledge of extracting or writing information from and to the PCM of a vehicle.
I have B&B Electronics interface to communicate with the PCM. But, use of it is poorly documented, and I've only gotten around to learning it enough to get basic information from the PCM. There's no real SDK I could find for programming using their adapter. I had to use the generic Microsoft serial commnications control to do that.