OK, hopefully I can explain this correctly.

Is it common with the 4l80 and 6.0l tranny engine combo to:

lets say your going down the road at 50mph in Drive or 4th gear
you press accelerator all the way down, the tranny downshifts to 3rd (sometimes 2nd). when it downshifts to 3rd the initial rpm is about 3500(not exact just an example) then it dips another 100-200rpm before it starts climbing/accelerating. Is this normal?

Can the dealer adjust the accelerator pedal sensitivity?
I have to push the pedal quite a ways down accelerating from a stop and to the floor to get a downshift.

 

That sounds about the way my truck responded when it was stock. I don't think the dealer can do anything for you. You can get this adjusted anyway you want by going with a custom tune.

 

on the downshifting thing, that's the tcc enguaging. as for how touchy it is, not much on that at this point.

 

I AM NOT SURE WHAT YEAR YOUR TRUCK IS BUT WE SEE QUITE A FEW VEHICLES COME THROUGH OUR SERVICE DEPARTMENT WITH COMPLAINTS OF POOR ACCELERATION & POOR DOWNSHIFT RESPONSE. IF IT SEEMS THAT YOU HAVE TO APPLY AN UNUSUAL AMOUNT OF PEDAL EFFORT TO INITIATE DOWNSHIFT & WIDE OPEN THROTTLE DOES NOT GIVE YOU AS MUCH PERFORMANCE AS YOU ACCUSTOM TO YOU PROBABLY HAVE A PROBLEM WITH THE PCM'S INDICATED THROTTLE ANGLE. I SEE THIS ABOUT ONCE A WEEK HEAR AT THE DEALERSHIP. YOU WILL NEED TO HOOK UP A TECH 2 & GO TO DATA DISPLAY FOR TRANSMISSION. AT THE TOP WILL TELL YOU INDICATED THROTTLE ANGLE. PUSH THE ACCELERATOR TO THE FLOOR & IT SHOULD READ 100%. IF IT DOES NOT THAN THAT TELLS YOU THE PCM IS NOT GETTING AN ACCURATE READING. TYPICALLY YOU CAN PULL THE GAS PEDAL FAIRLY HARD UPWARDS TO CORRECT IT.