For the 2023 M3 vehicles it's no easy task to get through the firewall (misnomer - no heat from ICE). For all the older year cars, there are several holes and plugs to punch through. For 2023 all the holes are gone. There are two large grommets up under the dash. The one on the right (passenger side) that most videos have suggested using but has a large conduit through which many wires run. It's also partially blocked by the MCU enclosure. I found that the grommet on the left (driver's side) is less populated. Only problem is that it's a little hard to get to without removing some of the trim, and you can't see the side facing the frunk. I have a flexible borescope so I could see the "fish" wire passing through. I have seen some people go along outer side of the grommet -- bad idea. I have seen people go through the main part of the grommet -- not so bad, but a little too close to the big fat power wire (I assume). You may notice that there are dimples around the periphery of the grommet that I recommend piercing, just don't push too hard otherwise the grommet dislodges. Then there is the problem of the yellow video cable connector. You need a pretty big hole to get it through. I cut the cable and then reattached the individual wires, but I doubt if anyone wants to do that. The second option, listed above, might be your best bet. Just remember the main cable goes to the passenger side to connect to the big light blue communications connector.