Need Advice: No Low-End Power from 5.3L

I need to know if the issue i'm facing is common for GM trucks, and if not any idea on what can cause it.

A few weeks ago i asked the dealer to check into why my Truck was getting such bad fuel milage. The dealer did a computer update, which seems to of solved the issue. However now i'm not getting any low end torque out of my truck. ( commented on in another thread)

Example: This weekend i was at my ranch, and there is a fairly steep hill leading up to a gate which i had to park at to unlock the gate. Once i got the gate open i hopped back in my truck put her in D and hit the gas, The engine just went to 1500 or so RPM but never moved. I let off the gas, check my emergency brake, and this time gave it the beans, again the engine just wen to about 1500rpm and sounded like it was bogged down. It never even spun a tire. So i figured maybe its traction control, so i turned that off and tried again, Nothing! So i rolled down the hill and had to get a running start with the foot to the floor. When i topped the hill I did a little more tested which i tried to do a little power brake maneuver in the dirt, and the truck just bogged down and never even spun a tire.

I've never seen this type of issue on a truck before, my dodge ram would burn the tires slap off if i punched it from a dead stop and it had 75 less HP ( 360 cu inch ).

I guess i really never try to "Hotrod" my truck, because I just see no point in such a large vehicle, but i would expect that 315hp should be able to spin a tire in the dirt, or get me up a hill.

I hope somebody has some suggestion, I'm going to try and get ahold of the dealer soon and they tend to work better if they know what there looking for.

Cheers and thanks in advance!