Hello fellas, Hope everyone is well.

I just performed a EGR Valve cleaning and EGR cooler Cleaning on my 2014 Ram 2500. It has 127K miles and from the looks of it, it had not been performed by previous owner, I'm guessing.
I bought it with 108K miles about 15 months ago.

I also replaced the Crank Case Filter as well.

I finished putting things back together and did the best to top of the coolant and remove excess air in the system, but now when I run it (no towing) I hear the normal Exhaust Brake noise turn on, but inside the cabin as if it's coming from the center of the dashboard, I hear a little bit of "hissing" like air being pushed out from somewhere.

Has someone encountered this before and what could it be? I'm hoping it's nothing major (fingers crossed) and I'm looking for some answers because in about 2 days I'm towing our family's travel trailer and I don't want any surprises on the way!

Thanks everyone for your help in advance.

Alex