oreo123 wrote:

....
Its a 3 family house with kitchs and baths on their own stack. This is top
floor unit where a non bearing wall was moved to reroute a vent stack. Issue
is with kitchen sink where it runs fine for first few gallons and then
stops. Get some bubbles and a very slow flow. Snaked it out to 25 feet 3
different times and no blockages. The 2 floors beneath have no issues. So I
wanted to draw it out and run it by a few people to get their wild guesses
before we start ripping things open.

If it's just this one sink in all likelihood there's a long horizontal
run or a sharp elbow somewhere and it has collected detritus from the
sink. Is possible that a vent is clogged, but much less likely imo.
I'm betting there's a clog past where your snake has reached.