On my 67 Coronet 383. My car has a nasty vibration at a specific engine RPM. It happens in the driveway parked, It happens driving down the road at exactly 1100 RPM. The steering wheel shakes violently and then it goes away with higher engine RPM. 1100 RPM is exactly at 30 mph and driving thru town sucks with a steering wheel shaking your fingers numb.
I removed the belt to the power steering pump and the vibration is 90% gone at 1100 RPM! Is it possible that the pump is causing this vibration hydraulically?

Thoughts?
Thank you in advance.