I searched and could not find any S5 specific info.. I have a S5 TII with a straight 3" exhaust and the airpump was removed before I owned the car. I am going to block off the ACV whenever I get a chance to make some plates but as for now the large tube that used to connect into the air pump and feed the ACV is open and I just noticed that the pipe is not really sucking vacuum but more like puffing.. would it be a good idea to block this off? is it related to intake vacuum?

 

Cap it off, or unscrew the tube & make a block off plate. It most likely isn't hurting anything, but if your check valve behind the ACV is in bad shape, you'll have an exhaust leak up through the tube. It's a straight shot to the exhaust ports from there.

 

ahh, that could explain why the "puffing" noise kind of sounds like exhaust pulses, I thought maybe they were intake pulses. also at higher rpm I hear what sounds like an exhaust leak which isn't there at idle, kind of like a wastegate is opening up, but it's not that loud.
well, I will make a block off plate then.. also my turbo spools extremely slow, this could be a reason. (it's a brand new rebuild, I checked everything out and it's perfect, and my wastegate is functioning properly)