another source of vibration is a worn impeller/shaft, they usually don't wear evenly, and tend to flog out into an egg shaped hole, with progressivly worsening vibration over time.
I've been a bit slack latley with the pump mod (too many projects on the go) but after seeing a detailed exploded diagram of the Eheim pumps I would predict similar performance increases with the offset mod as I saw in mine.
I can "see" the valve assembly in my head, i just have to make the damn thing
