vaccum leak andauxilary air regulator

[nono54]

Hi there,

I have a 78 911 sc, and will driving i notice quite a lot of back firing, especially when down shifting .
the previous owner did installed some different cams so it might be coming from that.
but in the doubt,thinking it was a vacuum leak I sprayed some carb cleaner to see if i had a leak and I found out couple of spot where the rpm went from 1100+/_ to 1200+/_when spraying this with a delay of maybe 2 second
the spot where :

at the hose that connect to the auxiliary air regulator (behind the second injector on the right side of the engine.

at some hose going toward the injector on the left side of the engine there is a spot where three of them are connected together

and i think but will try again at the injection boot

the most noticeable was the first one , is it possible and normal if not how do you proceed to fix it and what kind of hose is that?

thanks in advance
Arnaud