They Stage 1+ E85 rocks many happy users if you are after more power this is the way to go, if you want more power and more noise then stage 2 is the route I would go. and if you are feeling really brave.. Stage 2 E85 will have you down in the mid 10's 100-200
This is highly unlikely to have been caused by the tyres especially with your setup, Many cars in the US that are running very different setups and running fine. It sounds like typical Audi rubbish fobbing you off. Fight this with them, it is not acceptable.
Feel free to send the video over, the ignition timing after let off is ok as I'm assuming you have added overun/pops and bangs. Yea we can most likely rule out fuel now, there can be other fuel system issues but less likely.
Ok, so you want to be logging RPM, throttle position, requested boost pressure and actual, you want these to match as close as possible.
Ignition retardd for 1-5 cylinders you are looking for 0 across the board with minor retardd occasionally on the odd one or two cylinders no more than 3...
The only real way to know what is going on is by logging the car, you can then see if it is hitting the requested boost if it is pulling any timing and what it is advancing to. I Must say though that early torque spike is nasty, take it easy until it is figured out.