I think, without a moonroof, the most common source of a leaky A-Pillar is from the windshield. I would check the seal around the windscreen to see if that is how the water is getting in.I have a similar issue! Mine leaks on the driver side (A-Pillar) where the grab bar is, and the water comes out where the 'screw cover' is. What makes mine tough to diagnose is it does not leak every time it rains or gets wet, and I do NOT have a sunroof!!