Thanks for your insight, I understand a bit more what is happening now.
So if I understand correctly the Air parameter is mixing some of the dry signal with the cab signal.
I tried to add some Smoothing but it doesn't work.
Moving the time-alignment of the cab changes how the air react but it doesn't seems possible to align it perfectly to the dry signal as the cab signal has this leading silence and we can't move it back in time.
I guess the ideal would be to be able to time-align the dry signal going into the Air parameter to the cab signal but it doesn't seems to be possible as it is.
@Rex I answered in the original thread
@Moondog Wily thanks for the compliments !