I opened a stock bin for my K1500, and here is the settings for my "stock" 16168625 $E6.

TPS for EGR 2.4%

Maximum TPS for EGR enable 64.8%

Lower Map for EGR on 24.4 kpa

Upper Map for EGR on 96.3

For EGR to be enabled (or disabled for that matter), there are a lot more parameters to qualify ON or Off or even partial flow in the bin I have opened. And likely your bin as well.

So for the 4 listed above:
Any TPS between 2.4% and 64.8% qualifies for egr flow...
Then any map (VAC) reading between 96.3 kpa and 24.4 kpa qualifies for egr flow.

So the settings in your bin appear to have been modified for little to no flow. At 80% tps and between 30 and 38 kps you qualify for egr flow? I can't see that being correct.

How do they test your vehicle? Visual, Idle or on a tread mill for part throttle cruise? 4 gas analyzer or just pull codes?