I have a 2011 z71 1500 with the 5.3 afm flex fuel. Has 241,00 miles on it. I’m having a throttle issue. Around 1/4 throttle maybe a little less it has a bad lag. Almost like it’s running out of gas. Only way to get it to come out of it is either get going fast enough for the rpm’s to come up or gas it hard enough for the trans to kick down. If you drive it kind of hard it will get on through it and it won’t do it until you reach crushing speed and start backing off the throttle. The tps and pedal switch are working together. Fuel pressure is 43-46 at operating temp. The ignition timing during driving fluctuates from 40 to -10. Goes into the negatives when it starts acting up. The map sensor is at 7.1. Maf is at 9.7. Iv replaced the throttle body. The tps. The temp sensor. Spark plugs. Had the converters removed. The afm has been disabled. I’m at a loss on it. I can’t figure it out.

 

Did you try new wires?
mine was doing that. Around 1K rpm just cruising along it would start stumbling. I thought my year old tranny replacement was already acting up.
Swapped wires with cheaper Amazon find and problem went away.
My garage guy said it's known as miss fire under load