I recently installed Studor Mini-Vent air admittance valves (AAVs) in my attic on the two secondary (2 inch) plumbing vents (serving laundry room and kitchen) so that the vents no longer penetrate the roof. After doing this, my kitchen sink gurgles whenever the clothes washer drains into the laundry standpipe. If I remove the AAV on the laundry vent, the gurgling no longer happens, so it doesn't seem like there is a blocked vent.
I tested the AAV with my mouth and it seems to be working properly.
My only guess is that the AAVs require more pressure to open than the pressure required to gurgle the sink. Should I look for "weaker" AAVs? Would installing an AAV by the kitchen sink help eliminate the gurgling?