I have some experience with the spoiler/ASR issue when adding an aftermarket GT wing to a 2009 R8 V8.
Coding out the spoiler with VCDS makes the car go into an ASR/ESP protective mode at speed as described earlier in this thread. Apparently when no spoiler is installed the electronics are programmed to protect the driver from this dangerous situation by forcing ASR On. This would be A Good Thing if there were really no rear aero device installed. Unfortunately, the car doesn't know there is a GT wing present.
This is not a problem when the car is street-driven. Coding out the spoiler is a satisfactory solution in this situation.
When we want less ASR intervention (when driving aggressively on the track) it becomes very obtrusive. Hit the button to turn ASR off, and it turns on again by the next corner. I rode passenger in the car and watched the DIS and ASR light. It's very obvious tha is what's happening. To keep ASR off I had to press the button between every corner!
To determine if the spoiler is up, the system wants the spoiler motor to actually run, followed by a spoiler limit switch Up indication. This sequence turns on the spoiler light in the button and now the car is happy. So the problem to be solved is how do we get the spoiler light to turn On when the spoiler is actually locked down (which we've done to avoid interfering with the fixed GT-ish wing)?
To get an Up indication when the spoiler is actually down, I simply reversed the spoiler motor leads. Now we start the car and hold down the spoiler button, the motor runs up (actually down) and hits the internal limit switch (physically the down limit, but because we've swapped the wires the car thinks the spoiler is Up). The spoiler indicator light on the console turns On, and the car is happy. Because we've run the spoiler "up" manually using the button, it stays "up" until the car is turned off. With the spoiler light On, the driver again has normal control of ASR/ESP.
It's been some time since I worked on this, and I don't recall how we kept the spoiler from moving "down" (actually up) when the car slows. If I recall correctly, I think it simply stays "up" since the wing was "raised" manually using the button. I'll check when I'm again next to the car (might take a while) and I'll post an update if we took some additional steps.