avg. amount it lowered egt's ?
Probably 50 to 100 max.
I have always found it hard to quantify egt's. Day to day variations in heat and humidity make as much or more difference.
With the new cac there is a noticeable difference in how long it takes to hear up and cool down ie..longer to heat soak and faster to shed the heat load.
On a similar thread a poster described it as more hp at the same egt. This is what I think I am experiencing.
When I put an aftermarket cac on my dodge the effect was more noticeable but I already had high egt's so it is not apples to apples. I also used a different aftermarket manufacturer on each truck.
On both the dodge and the chevy I have noticed an increase of about 1 to2 mpg with the bigger cac not expected but a pleasant surprise.
for what it is worth
jim