6.2 in my truck..down on power?

[farmtruc]

Timing will depend on fuel octane and quality. 16deg is on the low side, but if the tuner is detecting and hearing detonation, nothing he can do; could be carbon build up, fuel, just one of those OS'.
6.2's like the high side of the rpm band, add a cam and it extends even further.
Truck shouldn't be gutless tho.

[jmro]

With it being 16, something may be wrong. These engines normally like to run mid to upper 20's some around 30ish. There are several threads on timing over on ls1tech.
Do you trust the person that did the tuning?