Air Intake Water Overflow

Late last year the jets in my pool began putting out significantly less pressure than when originally installed. When I started the pump up this year, the same limited pressure was observed but now the air intake was overflowing with water. This only occurs when the jet pump is on. When it is off the water recedes to approximately half way up the air intake (PVC tube). When initially installed there was no water in the air intake and the jets and venturi effect worked as it should.
In an effort to fix the problem I have:
-Removed the jets and checked for blockage or damage.
-Used a shop vac in exhaust mode to blow through air intake.
-Run the pump for over an hour in attempt to blow out anything that may be obstructing the flow.
-Run the pump with jet assemblies removed.

Nothing has worked.