tangcla wrote:I was told that the AVCS timing shouldn't be changed, as it's quite good from the factory...
I'd say that's from a tuner that's possibly not confident with moving the AVC-S timing around to get different responses from the engines power delivery.
Different tuners take different approach and use different ways to get there. Some tune against AFR (fattening up the mixture to get a little more torque, or remove det or cool the cylinders) while others tune with boost, AVC-S, timing, etc. It really depends on how smart the tuner is and how well you tell them what you want.
If you want meaty torque from down low, the tuner would be well advised to bring on AVC-S earlier to up the airflow to the turbo and bring spool on a lot sooner. Couple this with solid breathing mods (intake, exhaust) and you'll have a great little around towner with very strong and flat torque delivery.