I have a 2018 suburban and the low speed (under 40mph) throttle response is not linear or consistent. The transmission shifting also leaves much to be desired. is there a TSB or updated software available at the GM dealer. I have taken it to the dealer twice and they "cannot duplicate the problem" and found no issues. I have 6000 miles on a new vehicle and it behaves very poorly and also shifts down very hard on occasion.

 

Welcome to the forum.
also welcome to the "We can't design transmission software to shift normally" club. I experienced the same thing with my 2007 and 2010 Tahoes. It seems like it was reluctant to downshift and when you give it a little more gas all of a sudden it would downshift two gears. They also have an extreme amount of torque management that makes it hard to accelerate hard from a dead stop. It sounds like the same problem carried over into the new design Tahoes.