Hopefully this is the right sub-forum... I bought my 2006.5 GTI a few months back and it had the APR ECU upgrade pre-installed. Mode 1 was stock, Mode 2 was 91 octane , mode 3 was 93 octane, mode 4 was 100 octane I think. I normally ran the car in mode 2 and always pumped at least 91 octane...