isx15 bubbles

[Justinmakuch]

i have a 2008 isx15 that has been deleted for approx. 5 years now with no issues up until now.
the truck does not over heat but blows coolant out of the degas bottles, i assumed i had a head gasket issue, so i proceeded to do a combustion leak check. the fluid did not change color but when i snap the throttle i have bubbles on decel only not on accel.

*truck still has factory turbo
*egr is blocked off
*cap is new

i tried to attach a video for a visual
any input or idea would be great. i still believe i have a head gasket problem but what to rule out other options before i pull it apart

thanks in advance