I've just come across this thread as I was looking for clues on how to switch to cold start mode on demand.
I have a Capristo exhaust on my RS5 but I do not have the optional manual control box because I want the car to control the exhaust so it is noisy in Dynamic mode but quiet in Comfort mode. And most importantly when left in "AUTO" the car will switch between them depending on how you are driving. The Capristo control box in contrast, decides for itself what it wants to do (although it is programmable) but it does have the option on the remote control to "open the valves fully" and that switches it to cold start mode which was quite tempting I admit! It was also an additional £700 which was not so...
When the car starts from cold the noise is phenomenal and occasionally one has a desire to engage this when cruising town
The Capristo must be different to the standard exhaust because in Dynamic mode the valves are actually fully open, yet when the cold start is running it makes a lot MORE noise so there must be some other valves in there somewhere.
Does anyone know what happens in cold start in terms of what signals are sent where in order to make this happen?
There is a two wire plug in my boot next to a vacuum storage bottle thing. If I unplug this wire then the exhaust valves stay where they are no matter what. If you disconnect in Dynamic they stay open if you switch to Comfort and if you disconnect in Comfort mode they stay closed if you switch to Dynamic mode. So that all makes sense.
Now - if you disconnect the wire before starting the engine from cold, it never switches to cold start noise, it just stays the same as in Dynamic mode when the car is warmed up. However, if I start the car from cold and then disconnect the wire during the cold start noise period then it stays at full noisy. That's a bit confusing if the same wire pair controls the normal and cold start valve. Isn't it?
So I could run a wire to a switch on the dash to make or break that connection, but this wouldn't allow me to select cold start mode at will because it only ever happens when the engine starts from cold after it has been parked for a few hours.
Any clues welcome.
Incidentally, although the car does make sweet music when you use Dynamic mode and especially the "BRAP!" you get with any manual or auto change down, it is not intrusive when you are cruising and if you want quiet, you just switch to Comfort mode anyway and then it sounds pretty much standard really. Very useful for overtaking horses!
bit far for me. Will look about though. Save me leaving these valves unplugged. 
