Static in radio while driving

I picked up a used '09 Tacoma the other week and recently noticed that while driving there's a little static in the FM radio. At first I thought it was just a weak signal but then I realized that the static occurs on all stations, even the strong ones, and appears to be in rhythm with the movement of the antenna. I checked all the connections and they're good, antenna is in tight. Had the ground cleaned up and the radio comes in louder and clearer, but still has the same static while driving. Comes in crystal clear while parked. Going to try switching the antenna out with a friends '08 tonight and see if that changes anything. Any other ideas? Thanks!

It's the TRD Sport with the JBL upgrade, all factory installed parts.