strange whoosh + overboost ... hard to explain

while driving to work today, i noticed something off w/ car.

i was doing runs last night and the car was working flawlessly (cobb S1+aggST)

note: i have ER chargepipe w/ tial bov.

so, if i accelerate and quickly let off gas, there is a whoosh sound (not bov sound) as if it was not venting properly. immediately following the sound, i notice that rpm's bounce upward for a second as if overboost was forcing way into the combustion process. sorry but the issue is very hard to describe.

i attempted to log but couldnt get anything reliable on way to work. no codes thrown. will try to get some reliable logs tonight.

i plan on checking vacuum lines and bov tonight and see what i can find.

anyone have experience w/ any issues like this? any ideas?

thanks.