well i just got back from my tuner. truck is a nnbs 08 sierra with a gen 3 lq4 and 4l80e. reluctor was swapped 08 van 4l80e tcm, modded harness for 4l80e, e38 ecm and all tht good stuff to make it all gen 4. anyways, truck drives fine regular street driving it shifts nicely. however, went to get a retune since i added a 228r cam and it was a whole new ecu, and 1-2 shift at wot it shifts good. however, when i go wot from a higher roll like a 45 or 50, as soon as its gonna shift to 3, 2-3 shift, its as if i were letting go of the pedal. it flashes from 6k rpm down to about 4.5k rpm and then goes back to normal real fast. tuner says that for some reason the butterfly is closing when going into 3rd at wot that its going into some sort of limp mode. could my tb be messed up or what are the thoughts? thanks.

 

Would really need to see a log of what it is doing and the tune to be able to tell. Don't think it would be a TB problem...