I think I have confused you slightly.
I don't have the official 'Alpine Upgrade Kit' which is supplied by dealers etc...
I have an aftermarket 4 channel Alpine Amp (F640) which I have installed myself using the same logic/Instructions as supplied with the official Alpine Upgrade. For Example, I have made my own wiring loom but connected it at the same points as the Alpine upgrade kit.
What I want to know is; if you use an aftermarket Amp as I have done, how do you connect it to the HU after it has been coded to Hi-Fi??
I understand the Amp in the Alpine upgrade Kit has a switch on the bottom to set the Input from Low level to high level, depending on the Headunit outputs but an aftermaret amp such as mine doesnt have this feature.
BMW 330d M Sport, Spider Performance Tuning Box (est 280bhp), Body Colour grill (Mustache only), Carbon alloy center badges, Alpine and MB Quart Custom Audio.