Hey Gord, I can't complain about the wait bro, no worries. I've not ventured into the M yet for measurements or anything. I've been too busy myself and was hoping the Service Manual was coming out in May as promised, but nothing yet.

Whenever you can get to it bro, and TNX.

Colin.

 

Use a sharp 3/8" drill bit and a some pressure and it goes through the rubber easily. Created a very clean hole that the grounding wire easily passed through with a little lube (your choice ) I drilled 2 holes with no problems and the install looks very clean and professional. The same technique worked when putting a hole in the wire grommet for the ECU ground. Very easy to do and a very clean install look and a perfect seal.

 

Yes, I recommend using a 1/4" to 3/8" bit. Never had a problem drilling through the rubber. Using a bit that is slightly smaller and some lube (saliva works great), ensures that the grommet will seal tightly around the cable.

I used to just recommend using a sharp utility knife in the instructions, but some were making the hole too large and it was difficult to seal which became more important with the ECU wire pass-through into the passenger compartment. The drill bit makes for a more consistent and controllable result.