Hi DrG
The connections are no different to the MK7. The Helix comes with everything required, including the harness.
In summary:
1) Remove the long air vent dash trim - it’s on clips
2) Remove glovebox - 3 screws on bottom, 2 at top and one under the passenger airbag deactivication switch panel on side of dash
3) Disconnect battery or remove fuse
4) Remove two MIB unit retaining screws and hinge down the MIB unit
5) Release the MIB unit using radio release tools.
6) Follow Helix kit wiring instructions - power cables de-pin from car harness and fit to new harness. New power cables from new harness fit to car harness. Release brown speaker wiring block from car harness and fit to new harness, and replace with brown speaker block from new harness. I think that’s it from memory. Many online videos available.
7) Feed new harness behind the MIB and down the passenger side of car, under the sill trims, to the boot.
8. On the GTI the subwoofer secures on top of the space saver if you have one. An extension plastic securing both is required from VW. As with the MK7, the boot floor sits very slightly proud, but I placed some stoppers on the rear edge so it doesn’t rest on the subwoofer.
9) Program using a dongle - I found the MK7 5 door works well, with a few tweaks in the car sound settings - pushed the centre to the rear slightly too.
Hopefully I haven’t missed too much.
All speakers worked, but please be aware that I might have just been lucky with my setup. It’s a 2022 pre-facelift, with my centre speaker upgrade and Focal door speakers.
In my view the first upgrade whether you have the HK system or not is the centre speaker.
https://www.golfgtiforum.co.uk/index.php?topic=291139.0If you are feeling brave, and can source a Helix kit, go for it, but please note my caveats above - I could not trace anyone who has previously done this so I’m possibly one of one and it worked!
I sourced my kit from a forum member.
Cheers