An indication of why people fail the AQC would be of interest,
Lack of recent flying practice and rusty instrument flying skills. There's a lot to learn on the AQC and you do not have the time to re-learn how to fly an ILS or how to deal with an engine failure. The Boeing 737 is a twin engine aircraft and you need exactly the same skills to fly it as you do a Duchess or a Seneca. If you are in doubt about your skills I recommend getting some sim time with an instructor. Do not bother wasting money on a jet sim, a FNPT2 will be good enough.
SW