To tune these you need to make use of boost gauge, and either an EGT gauge, or an AFR gauge.
If they aren't using gauges, they are really fxcking with what they don't understand.
Yes, you can tune by the seat of the pants, but they either be leaving potential power on the table, or compromising economy for power, and putting engine and turbo at risk from high EGTs.
There's a fine line between tuning for power and running too hot.
This needs to be tested with the engine under load. The only way to test is with gauges, or dyno and gauges.
Same with timing the pump. You can take a stab at it with trial and error, but without starting from a factory baseline, they are flying blind.
Honestly, if I had a customer's rig for 6 months without an awesome result, I'd quit my job and go and pack supermarket shelves for a living or get a job licking windows.
Sorry to be harsh, but that's just embarassing.
As usual, I agree with you. The only thing I'd add is that tuning these things is really easy. The diesel crowd here helped me get mine tuned easily.
@ubguessin Get compression numbers first.
Then get your gauges in and the guys here can help you get tuned. A quick video showing the issue might help too.