Loss of low end torque

I have a 2006 2500 avy and I feel like the truck has lost some low end torque. When I start the truck I let it idle for 5 minutes I and then I drive  . When I give it gas the rose start to climb but truck is lazy to move and when I continue to accelerate it picks up . I?m not sure why it?s lazy off the line . I was told it?s torque management Chevy put in these trucks . I installed a cai and cleaned the mass air sensor the cai filter is two years old but looked ok . I?m towing in a couple weeks and am concerned about the towing power. Any advise is appreciated

tranny issues?

How many miles on the truck? Enough that the catalytic converters could be clogging?

It has around 121000 miles . I did smell rotten eggs like a couple months ago

Bingo!!!

clogged cats usually restrict upper RPM since exhaust cannot get out.

I would have truck scanned for codes and checked out by mechanic