good vibrations, not so much

Boat: 08 Sanger V215 black scorpion 330 (110 hrs)

So I took the boat out today for the first time in a few months to run it, check fluid levels, perfect pass after servo replacement, and what not to ensure no surprises for our upcoming river trip. I noticed a small vibration while running at wakeboading speed (22 mph / 2500ish rpm). The vibration was running through the hull. My first thought would be the prop or shaft, but the vibration would go away at higher rpms (30 mph 3000ish rpms). Which made me think the motor might just be running a little rough at the lower rpms and it is resonating through the hull. The motor recently had an exhaust leak on the heads (gasket) that was fixed under warranty.

Now the problem, was this vibration always there and I am being sensitive because haven't had it out in a few months, or is something brewing that I need to tend to. the vibration wasn't so severe I was concerned and stopped running it, but I don't want an easy fix now turn into a more expensive fix later. Plus it is simply a little annoying. Any thoughts or suggestions.