A8 Parts Forum - Engine vacuum low and SAI issues

Apologies for the long ramble here. Bit of an issue with my SAI system, etc. When I got the car a few weeks ago first thing I did was replaced my bad SAI pump, which is now working as it should near as I can tell. Thing is though, I keep getting the codes for secondary air pump low flow both banks, always both banks. I've checked all the vac lines and replaced most of them for good measure. I've verified the combination valve (selenoid?) is working and both vaccum canisters hold vacuum just fine, fuses and relay are ok. I think though, that the reason my "canisters" (sorry wrong term) aren't opening is that I'm lacking enough engine vacuum to open them? I measured the vacuum on the line that goes to the selenoid valve (combi?) and I'm only reading 3" of vacuum at idle? Pretty sure the guage is ok as I can crank it up nearly to the max just sucking on it. I did a primitive vacuum test upstream on the same line (away from engine) and it seems to be holding vacuum there also. Tho it acts like I'm putting vacuum to a rather large space, takes a while to build up but does hold. Anyone have any idea what could be going on here? I seriously doubt my engine is kaput because well, it's got plenty of power. Also, another clue... I know those front vaccum cans on the front of the engine related to "flaps" were previously closing at idle and open with engine off and the arms moved ok. NOW... they aren't closing at idle, they're just a tiny bit collapsed, each one equally but definitely not closing. So seems like I have a vacuum leak somewhere, but what's confusing is the system going back away from the engine from the selenoid holds vacuum? Kinda lost here, thanks for any ideas.