Hey Larry, sounds like you're deep into tweaking the audio DSP pipeline on your High Sierra MacBook Pro—removing that aggressive dynamic range compression is such a practical goal. Let’s walk through the most likely culprits for your kext failing to load, even after disabling SIP and stripping the signature:

1. Double-Check SIP is Fully Disabled #

It’s easy to assume SIP is off, but partial disabling won’t cut it for low-level kext modifications. Boot into Recovery Mode (hold Command+R on startup), open Terminal, and run:
csrutil status
Make sure it returns System Integrity Protection status: disabled. If it shows any enabled exceptions, run csrutil disable and reboot fully before testing your modified kext again.

2. Fix Kext Packaging & Permissions #

Even tiny permission missteps can break kext loading. When repackaging your modified AppleHDA.kext:

• Set the correct owner and group with:
  sudo chown -R root:wheel /path/to/modified/AppleHDA.kext
• Set proper file permissions:
  sudo chmod -R 755 /path/to/modified/AppleHDA.kext
• Avoid regular zip tools—use ditto for safe packaging:
  ditto -ck --sequesterRsrc --keepParent AppleHDA.kext AppleHDA-modified.zip
  Then extract it to your target location with:
  ditto -xk AppleHDA-modified.zip /Library/Extensions

3. Confirm You’re Editing the Right Plist for Your Model #

High Sierra’s AppleHDA uses model-specific audio layouts, so targeting the wrong plist can break loading and ignore your changes. First, find your MacBookPro13,2’s layout ID:

• Boot into macOS, open Terminal, run:
  ioreg -l | grep -i "layout-id"
• Match that ID to the corresponding plist in AppleHDA.kext/Contents/Resources/ (look for files like layoutX.xml.zlib where X is your layout ID). If you edited generic plists instead of this model-specific one, the kext will reject your changes.

4. Diagnose Exact Loading Errors with kextutil #

Stop guessing—let macOS tell you what’s broken. Run this command in Terminal (replace the path with your modified kext’s location):
sudo kextutil -v /Library/Extensions/AppleHDA.kext
This will spit out detailed logs, flagging issues like invalid plist syntax, missing dependencies, or corrupted resources. Fix any errors it reports before retrying.

5. Clear Kernel Caches & Reboot #

Old cached kext data can override your modified version. Clear the cache with:
sudo kextcache -invalidate /
Then reboot. For extra measure, boot into Safe Mode (hold Shift on startup) once to force a full cache rebuild.

6. Ensure Signature is Fully Stripped #

Sometimes signature remnants linger even after you try to remove them. Check with:
codesign -dv --verbose=4 /path/to/AppleHDA.kext
If any signature metadata shows up, fully strip it with:
sudo codesign --remove-signature /path/to/AppleHDA.kext
Then reapply the correct permissions (step 2) before testing.

内容的提问来源于stack exchange，提问作者Larry Chen