The speed thing is easy:
- Get Silent 3ditor(S3D)
- Backup your SH4/Data/Library/Torpedoes_US.sim and open it with S3D
- Adjust the speed and range of the very first entry(amun_AcousticTorpedo). It's the Mk27.
- Save and have fun with it!
The guidance part, I have no idea.