I lost the bonding of the wing pressure sensors to the wing. It was a minute leak, but until I found that it messed up my AoA. The way to check is to tape the ports up and then disconect the blue and green tubes, and suck.
This may not be your problem, but I just went through a similar experience. It seemed that my AOA had lost its calibration and would give me a stall warning at around 70 mph.
It turned out that the Vans (UMA) airspeed indicator was reading 20 mph higher than my actual airspeed. The instrument shop said that the diaphragm was deformed and it could not be recalibrated. Installed a new airspeed indicator and the problem was solved. AOA calibration was never the problem.