Kitchen double sink backing up slowly on each side

[HuddleHouse]

I plunged each side of sink up top... disconnected trap below and ran water from each side. Water ran out fine so problem not here.
I ran a 3 to 4 ft snake down pipe going into wall under vent and no blockage. My problem is when i start to run sink water backs up and out the Proflo vent seen in picture.
Any advice? Is it a gravity (vacuum) issue or is the clog lower in the pipe under vent going into wall??

Thanks,
Huddle

 

[rpm]

Did you actually clean the trap when it was removed and perhaps lift the nearest manhole cover and take a peek for problem there.
Is that a sink muncher in the photo to the right?

 

[HuddleHouse]

Did you actually clean the trap when it was removed and perhaps lift the nearest manhole cover and take a peek for problem there.
Is that a sink muncher in the photo to the right?

yes the trap is clean & yes that is a disposal on the right.
Everything is clear down to where the trap runs into the pipe under the vent.
I only have a 3 ft snake (for toilet) but i ran it down that pipe (under vent) as far as i could and it was clear as well.

Huddle