Big Block:
I have tuned an 04 AWD Denali with the LQ4 and an 06 GTO with the LS2, and an 05 Sierra 1500 2WD with an LQ9. The owners of all 3 were very happy with the improvements. My tuning nets people 2 more mpg (normally), gets them a lot more throttle response, firms up the shifts, shifts happen at the right RPM and speed throughout the pedal position, and it puts out a little more power. I never send out scripts for gas tunes and I never send out a tune that was written for someone else's truck; each tune is written from that vehicle's stock tune - so while I do have LQ9 tunes I won't have "yours" until you send me the stock tune and I make it.
Blownaway:
If you plan to own a Dmax and are hands on, there is no reason to not own EFI Live.